The following extract is from the article “Names of God” in The Jewish Encyclopedia, Isidore Singer (ed.), volume IX, pages 160-161.
Of the names of God in the Old Testament, that which occurs most frequently (6,823 times) is the so-called Tetragrammaton, YHWH (יהוה), the distinctive personal name of the God of Israel. This name is commonly represented in modern translations by the form “Jehovah,” which, however, is a philological impossibility (see Jehovah). This form has arisen through attempting to pronounce the consonants of the name with the vowels of Adonai (אדני = “Lord”), which the Masorites have inserted in the text, indicating thereby that Adonai was to be read (as a “ḳeri perpetuum”) instead of YHWH. When the name Adonai itself precedes, to avoid repetition of this name, YHWH is written by the Masorites with the vowels of Elohim, in which case Elohim is read instead of YHWH. In consequence of this Masoretic reading the authorized and revised English versions (though not the American edition of the revised version) render YHWH by the word “Lord” in the great majority of cases.
This name, according to the narrative in Ex. iii. (E), was made known to Moses in a vision at Horeb. In another, parallel narrative (Ex. vi. 2, 3, P) it is stated that the name was not known to the Patriarchs. It is used by one of the documentary sources of Genesis (J), but scarcely if at all by the others. Its use is avoided by some later writers also. It does not occur in Ecclesiastes, and in Daniel is found only in ch. ix. The writer of Chronicles shows a preference for the form Elohim, and in Ps. xlii.-lxxxiii. Elohim occurs much more frequently than YHWH, probably having been substituted in some places for the latter name, as in Ps. liii. (comp. Ps. xiv.).
In appearance, YHWH (יהוה) is the third person singular imperfect “ḳal” of the verb הוה (“to be”), meaning, therefore, “He is,” or “He will be,” or, perhaps, “He lives,” the root idea of the word being, probably, “to blow,” “to breathe,” and hence, “to live.” With this explanation agrees the meaning of the name given in Ex.iii.14, where God is represented as speaking, and hence as using the first person—“I am” (אהיה, from היה, the later equivalent of the archaic stem הוה). The meaning would, therefore, be “He who is self-existing, self-sufficient,” or, more concretely, “He who lives,” the abstract conception of pure existence being foreign to Hebrew thought. There is no doubt that the idea of life was intimately connected with the name YHWH from early times. He is the living God, as contrasted with the lifeless gods of the heathen, and He is the source and author of life (comp. I Kings xviii.; Isa. xli. 26-29, xliv. 6-20; Jer. x. 10, 14; Gen. ii. 7; etc.). So familiar is this conception of God to the Hebrew mind that it appears in the common formula of an oath, “ḥai YHWH” (= “as YHWH lives”; Ruth iii.13; I Sam.xiv.45; etc.).
If the explanation of the form above given be the true one, the original pronunciation must have been Yahweh (יַהְוֶה) or Yahaweh (יַהְַוֶה). From this the contracted form Jah or Yah (יָהּ) is most readily explained, and also the forms Jeho or Yeho (יְהוֹ = יְהַו = יַהְוְ), and Jo or Yo (יוֹ, contracted from יְהוֹ), which the word assumes in combination in the first part of compound proper names, and Yahu or Yah (יָהוּ = וַהְוְ) in the second part of such names. The fact may also be mentioned that in Samaritan poetry יהוה rimes with words similar in ending to Yahweh, and Theodoret (“Quæst. 15 in Exodum”) states that the Samaritans pronounced the name ’Iαβέ. Epiphanius ascribes the same pronunciation to an early Christian sect. Clement of Alexandria, still more exactly, pronounces ’Iαουέ or ’Iαουαί, and Origen, ‘Iαη. Aquila wrote the name in archaic Hebrew letters. In the Jewish-Egyptian magic-papyri it appears as Ιαωουηε. At least as early as the third century B.C. the name seems to have been regarded by the Jews as a “nomen ineffabile,” on the basis of a somewhat extreme interpretation of Ex. xx. 7 and Lev. xxiv. 11 (see Philo, “De Vita Mosis,” iii. 519, 529). Written only in consonants, the true pronunciation was forgotten by them.
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