Your inability to click on links and read stuff for yourself is rather sad. Do you want me to copy and paste for you?
The most widespread theory is that the Hebrew term ??????? has the vowel points of ??????? (adonai). Using the vowels of adonai, the composite hataf patah ? under the guttural alef ? becomes a sheva ? under the yod ? , the holam ? is placed over the first he ? , and the qamats ? is placed under the vav ? , giving ??????? (Jehovah). When the two names, ???? and ???? , occur together, the former is pointed with a hataf segol ? under the yod ? and a hiriq ? under the second he ? , giving ??????? , to indicate that it is to be read as (elohim) in order to avoid adonai being repeated. [ 23 ]
The pronunciation Jehovah is believed to have arisen through the introduction of vowels of the qere—the marginal notation used by the Masoretes. In places where the consonants of the text to be read (the qere) differed from the consonants of the written text (the kethib), they wrote the qere in the margin to indicate the desired reading.  In such cases, the kethib was read using the vowels of the qere. For a few very frequent words the marginal note was omitted, referred to as q're perpetuum. [ 17 ] One of these frequent cases was God's name, which was not to be pronounced in fear of profaning the "ineffable name". Instead, wherever ???? (YHWH) appears in the kethib of the biblical and liturgical books, it was to be read as ??????? (adonai, "My Lord [plural of majesty]"), or as ???????? (elohim, "God") if adonai appears next to it.  This combination produces ??????? (yehovah) and ??????? (yehovih) respectively.  ???? is also written ’? , or even ’? , and read ha-Shem ("the name"). [ 23 ]
Scholars are not in total agreement as to why ??????? does not have precisely the same vowel points as adonai.  The use of the composite hataf segol ? in cases where the name is to be read, "elohim", has led to the opinion that the composite hataf patah ? ought to have been used to indicate the reading, "adonai". It has been argued conversely that the disuse of the patah is consistent with the Babylonian system, in which the composite is uncommon. [ 23 ]