For anyone who is interested, here is the entire document from the Biblical Archaeology Review regarding God's name in the NT that renaii quoted from:
The Name of God in the New Testament
Did the earliest Gospels use Hebrew letters for the Tetragrammaton? By George Howard
Many early copies of the New Testament abbreviate sacred words (nomina sacra). The earliest of these abbreviations stand for “God,” “Lord,” “Christ,” and “Jesus.” Abbreviations of these words were formed by writing their first and last letters and placing a line over them. Thus, using English to illustrate, “God” would appear as G ÷ D ÷ and “Lord” as L ÷ D ÷ . The attempt to differentiate and dignify the sacred name of God goes back to pre-Christian times; it was done first by Jews. From the Dead Sea Scrolls we know that Jewish scribes often distinguished the divine name Yahweh. (Yahweh is known as the Tetragrammaton because it consists of four consonant Hebrew letters, yod, he, vav, he, often written in English YHWH.) Frequently, the scribes who wrote the Dead Sea Scrolls would write the Tetragrammaton in old paleo-Hebrew script, although the scroll was otherwise written in square Aramaic script. An example is the Habakkuk commentary found in cave 1. In the portion reproduced in the color photograph, the Tetragrammaton appears twice in paleo-Hebrew script on line 7 word 3 (reading from right to left) and on line 14 word 7. The rest of the text is in square Aramaic script—the same script used as a basis for writing Hebrew today. The Tetragrammaton is used in the Habakkuk commentary only in Biblical quotations. Whenever reference is made to God in the commentary portion, the generic word el (God) is used. This is true not only in the Habakkuk commentary, but in other Qumran (Dead Sea Scroll) documents as well. The Qumran covenanters had other devices for circumventing the use of God’s name. Sometimes they would write four or five dots in place of the Tetragrammaton. In the Community Rule, for example, the writer quotes Isaiah 40:3 as follows: “Prepare in the wilderness the way of . … ”. We know from the Masoretic Text that the four dots stand for the Tetragrammaton YHWH. This same passage is quoted again in a document discovered in Qumran Cave 4 (4QTanhumim) with four dots representing the divine name. At times, dots were placed above the Tetragrammaton when it had been written by mistake, apparently as a means of canceling the word without actually erasing it. Jews early adopted the practice of not pronouncing the divine name when Scripture was read aloud, even in prayer. The word adonai (Lord) was (and is to this day) read by Jews instead of the Tetragrammaton YHWH which appears on the page. Such practices as writing the divine name in archaic script, of substituting dots for it, or of avoiding it altogether suggests that to Jews the sacred name for God was a special word which required special treatment both in writing and oral reading. Christian Scriptures frequently quote passages from the Old Testament in which the divine name YHWH appears in the original Hebrew. In these quotations, however, the divine name is translated into the Greek word kyrios (Lord), or occasionally theos (God). Both of these words are generic words for God, not limited to the Hebrew God whose name is Yahweh and who is represented in the Hebrew Bible by the Tetragrammaton. Most of these Old Testament quotations in the New come from the Septuagint, a Greek translation of the Old Testament made by Jews in pre-Christian times. The Septuagint (or at least the extant, later Christian copies of it) usually renders the Tetragrammaton by kyrios; the New Testament simply follows this practice. In 1944, W. G. Waddell discovered the remains of an Egyptian papyrus scroll (Papyrus Fuad 266) dating to the first or second century B.C. which included part of the Septuagint. In no instance, however, was YHWH translated kyrios. Instead the Tetragrammaton itself—in square Aramaic letters—was written into the Greek text. This parallels the Qumran Covenanters’ use of the palaeo-Hebrew script for the Divine Name in a document which was otherwise written in square Aramaic script. An even closer parallel to the practice Waddell found in Papyrus Fuad 266 comes from second century A.D. Jewish translations of the Old Testament into Greek by Aquila, Symmachus, and Theodotion. In 1897, F. C. Burkitt published some fragments of Aquila’s Greek Old Testament which had been found in the debris of a geniza (a storeroom for worn out manuscripts) of the old synagogue in Cairo. These fragments which are the underwriting of palimpsest a scraps clearly show the Hebrew Tetragrammaton in paleo-Hebrew script written into the otherwise Greek text. A number of other similar examples have also come to light. 
At the end of the last century, Giovanni Cardinal Mercati discovered a palimpsest in the Ambrosian Library of Milan containing parts of the Psalter to Origen’s Hexapla b (lacking the Hebrew column). All the columns show the Tetragrammaton written in square Aramaic script, although the texts are otherwise written in Greek. Fragments of Psalm 22 from Origen’s Hexapla, found in the Cairo geniza, were published in 1900 by C. Taylor. These fragments show the Tetragrammaton written into the Greek columns of Aquila, Symmachus, and the Septuagint in the strange form of PIPI. This is a clumsy attempt to represent with Greek letters what the Tetragrammaton looked like in Hebrew. The Greek letter pi somewhat resembles the Hebrew letter he. The Fuad papyrus scroll is the earliest example we have examined, dating to the first or second century B.C. Here for the first time we have clear evidence that in pre-Christian times the Septuagint, at least sometimes, did not translate the divine name with the Greek word kyrios as had been thought; rather it preserved the Hebrew word YHWH itself. Could it be that Jews had always written the Tetragrammaton in Hebrew into the text of their Greek Bibles and that this practice represented a continuous tradition from the earliest Septuagint through the second century translations of Aquila, Symmachus, and Theodotion? Or is the Fuad manuscript a maverick, the only one in its day to do such a thing? In 1952, fragments of a scroll of the Twelve Prophets in Greek were found in a cave at Nahal Hever in the Judean Desert. Père D. Barthelemy announced the discovery of the scroll in 1953 and ten years later published a transcription of it. In all probability the document dates to the beginning of the first Christian century. Like the Fuad papyrus it too writes the Tetragrammaton in Hebrew—in old style script—in an otherwise Greek text. At Qumran cave 4, a fragment of the Greek translation of Leviticus confirms that the divine name was preserved in the pre-Christian Septuagint. In this scroll, dated by P. W. Skehan to the first century B.C., the Tetragrammaton is transliterated with the Greek letters IAO. Thus, we have three separate pre-Christian copies of the Greek Septuagint Bible and in not a single instance is the Tetragrammaton translated kyrios or for that matter translated at all. We can now say with near certainty that it was a Jewish practice before, during, and after the New Testament period to write the divine name in paleo-Hebrew or square Aramaic script or in transliteration right into the Greek text of Scripture. This presents a striking comparison with the Christian copies of the Septuagint and the quotations of it in the New Testament which translate the Tetragrammaton as kyrios or theos. Why do Christian copies of the Septuagint reflect a practice so radically different from that of the Jews in designating the Divine Name? Or do they? We have already mentioned that while Christians translated the Tetragrammaton as either kyrios or theos, they abbreviated these surrogates by writing only their first and last letters and by placing a line over them to attract attention. What was the purpose of these Christian abbreviations? In 1907, Ludwig Traube suggested that the nomina sacra were of Hellenistic Jewish origin. The first of these, he suggested, was theos, which was abbreviated without vowels so as to follow the Hebrew custom of writing consonants only. Soon theos was followed by kyrios which became an alternate surrogate and the first and last letters became an alternate contraction. According to Traube, these contractions gave rise to the belief that the important thing was to write sacred words in abbreviated form. This resulted in a number of words being written in a similar way (for example, spirit, father and heaven). In 1959, A. H. R. E. Paap took up the issue again and argued that the system of contracted nomina sacra was of Jewish-Christian origin emanating from Alexandria about 100 A.D. It seems to me, however, that a much better case can be made that the system of contractions is of Gentile Christian origin. The divine name YHWH was and is the most sacred word in the Hebrew language. So it is hardly likely that Jews of any sort would have removed it from their Bibles. Furthermore, we know now from discoveries in Egypt and the Judean desert that Jews wrote the Tetragrammaton in Hebrew even in their Greek texts. In all likelihood Jewish Christians felt the same way about the divine name and continued to preserve it in Hebrew in their Bibles. A famous rabbinic passage (Talmud Shabbat 13.5) discusses the problem of destroying heretical texts (very probably including books of Jewish-Christians). The problem arises for the rabbinic writer because the heretical texts contain the divine name, and their wholesale destruction would include the destruction of the divine name. This further suggests that Jewish Christians did not translate the divine name into Greek. But Gentile Christians, unlike Jewish Christians, had no traditional attachment to the Hebrew Tetragrammaton and no doubt often failed even to recognize it. Gentile scribes who had never before seen Hebrew writing (especially in its archaic form) could hardly be expected to preserve the divine name. Perhaps this contributed to the use of surrogates like kyrios and theos for the Tetragrammaton. The contracted form of the surrogates marked the sacred nature of the name standing behind them in a way which was convenient for Gentile scribes to write. At the same time the abbreviated surrogates may have appeased Jewish Christians who continued to feel the necessity of differentiating the divine name from the rest of the text. After the system of contractions was in use for some time, its purpose was forgotten and many other contracted words which had no connection with the Tetragrammaton were introduced. Assuming this to be generally correct, I offer the following scenario of the history of the Tetragrammaton in the Greek Bible as a whole, including both testaments. First, as to the Old Testament: Jewish scribes always preserved the Tetragrammaton in their copies of the Septuagint both before and after the New Testament period. In all probability Jewish Christians wrote the Tetragrammaton in Hebrew as well. Toward the end of the first Christian century, when the church had become predominantly Gentile, the motive for retaining the Hebrew name for God was lost and the words kyrios and theos were substituted for it in Christian copies of Old Testament Septuagints. Both kyrios and theos were written in abbreviated form in a conscious effort to preserve the sacred nature of the divine name. Soon the original significance of the contractions was lost and many other contracted words were added. A similar pattern probably evolved with respect to the New Testament. When the Septuagint which the New Testament church used and quoted contained the Hebrew form of the divine name, the New Testament writers no doubt included the Tetragrammaton in their quotations. But when the Hebrew form for the divine name was eliminated in favor of Greek substitutes in the Septuagint, it was eliminated also from the New Testament quotations of the Septuagint. Thus toward the end of the first Christian century, the use of surrogates (kyrios and theos) and their contractions must have crowded out the Hebrew Tetragrammaton in both Testaments. Before long the divine name was lost to the Gentile church except insofar as it was reflected in the contracted surrogates or remembered by scholars. Soon, even the contracted substitutes lost their original significance and were joined by a host of other abbreviated nomina sacra which had no connection with the divine name at all. Is there any way for us, at this late date, to calculate the effect which this change in the Bible had on the second century church? It is of course impossible to know with certainty, but the effect must have been significant. First, a number of passages must have taken on an ambiguity which the original lacked. For example, the second century church read, “The Lord said to my Lord” ( Matthew 22:44 , Mark 12:36 , Luke 20:42 ), a reading which is as ambiguous as it is imprecise. The first century church probably read, “YHWH said to my Lord.” To the second century church, “Prepare the way of the Lord” ( Mark 1:3 ) must have meant one thing, since it immediately followed the words: “The beginning of the gospel of Jesus Christ.” But to the First Century Church it must have meant something else since they read, “Prepare the way of YHWH.” The second century church read 1 Corinthians 1:31 , “The one who boasts, let him boast in the Lord,” which was probably considered a reference to Christ mentioned in verse 30 . But to the first century church, it probably referred to God mentioned in verse 29 since they read, “The one who boasts let him boast in YHWH.” These examples are sufficient to suggest that the removal of the Tetragrammaton from the New Testament and its replacement with the surrogates kyrios and theos blurred the original distinction between the Lord God and the Lord Christ, and in many passages made it impossible to tell which one was meant. This is supported by the fact that in a number of places where Old Testament quotations are cited, there is a confusion in the manuscript tradition whether to read God or Christ in the discussion surrounding the quotation. Once the Tetragrammaton was removed and replaced by the surrogate “Lord”, scribes were unsure whether “Lord” meant God or Christ. As time went on, these two figures were brought into even closer unity until it was often impossible to distinguish between them. Thus it may be that the removal of the Tetragrammaton contributed significantly to the later Christological and Trinitarian debates which plagued the church of the early Christian centuries. Whatever the case, the removal of the Tetragrammaton probably created a different theological climate from that which existed during the New Testament period of the first century. The Jewish God who had always been carefully distinguished from all others by the use of his Hebrew name lost some of his distinctiveness with the passing of the Tetragrammaton. How much He lost may be known only by the discovery of a first century New Testament in which the Hebrew name YHWH still appears. (For further details, see George Howard, “The Tetragram and the New Testament”, Journal of Biblical Literature 96 (1977) 63–83.)