Jewish Encyclopedia - JEHOVAH:
A mispronunciation (introduced by Christian theologians, but almost entirely disregarded by the Jews) of the Hebrew "Yhwh," the (ineffable) name of God (the Tetragrammaton or "Shem ha-Meforash"). This pronunciation is grammatically impossible; it arose through pronouncing the vowels of the "kere" (marginal reading of the Masorites: ???? = "Adonay") with the consonants of the "ketib" (text-reading: ???? = "Yhwh")—"Adonay" (the Lord) being substituted with one exception wherever Yhwh occurs in the Biblical and liturgical books. "Adonay" presents the vowels "shewa" (the composite under the guttural ? becomes simple under the ?), "holem," and "kamez," and these give the reading ????(= "Jehovah"). Sometimes, when the two names ???? and ???? occur together, the former is pointed with "hatef segol" () under the ? —thus, ???? (="Jehovah")—to indicate that in this combination it is to be pronounced "Elohim" ?????). These substitutions of "Adonay"and "Elohim" for Yhwh were devised to avoid the profanation of the Ineffable Name (hence ???? is also written ?, or even ?, and read "ha-Shem" = "the Name ").
The reading "Jehovah" is a comparatively recent invention. The earlier Christian commentators report that the Tetragrammaton was written but not pronounced by the Jews (see Theodoret, "Question. xv. in Ex." [Field, "Hexapla," i. 90, to Ex. vi. 3]; Jerome, "Præfatio Regnorum," and his letter to Marcellus, "Epistola," 136, where he notices that "PIPI" [= ΠIΠI = ????] is presented in Greek manuscripts; Origen, see "Hexapla" to Ps. lxxi. 18 and Isa. i. 2; comp. concordance to LXX. by Hatch and Redpath, under ΠIΠI, which occasionally takes the place of the usual κ?ριος, in Philo's Bible quotations; κ?ριος = "Adonay" is the regular translation; see also Aquila).
"Jehovah" is generally held to have been the invention of Pope Leo X.'s confessor, Peter Galatin ("De Arcanis Catholicæ Veritatis," 1518, folio xliii.), who was followed in the use of this hybrid form by Fagius (= Büchlein, 1504-49). Drusius (= Van der Driesche, 1550-1616) was the first to ascribe to Peter Galatin the use of "Jehovah," and this view has been taken since his days (comp. Hastings, "Dict. Bible," ii. 199, s.v. "God"; Gesenius-Buhl, "Handwörterb." 1899, p. 311; see Drusius on the tetragrammaton in his "Critici Sacri, i. 2, col. 344). But it seems that even before Galatin the name "Jehovah" had been in common use (see Drusius, l.c. notes to col. 351). It is found in Raymond Martin's "Pugio Fidei." written in 1270 (Paris, 1651, iii., pt. ii., ch. 3, p. 448; comp. T. Prat in "Dictionnaire de la Bible," s.v.). See also Names of God.
Jewish Encyclopedia-Names of God-YHWH. Of the names of God in the Old Testament, that which occurs most frequently (6,823 times) is the so-called Tetragrammaton, Yhwh (????), 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 (???? = "Lord"), which the Masorites have inserted in the text, indicating thereby that Adonai was to be read (as a "keri 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 (????) is the third person singular imperfect "kal" of the verb ( ??? ("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" (????, from ( ???, the later equivalent of the archaic stem ( ???). 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, "hai 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 ((????) or Yahaweh (????). From this the contracted form Jah or Yah (?? ) is most readily explained, and also the forms Jeho or Yeho (??? ), and Jo or Yo (?? contracted from ??? , which the word assumes in combination in the first part of compound proper names, and Yahu or Yah (??? ) in the second part of such names. The fact may also be mentioned that in Samaritan poetry ???? rimes with words similar in ending to Yahweh, and Theodoret ("Quæst. 15 in Exodum") states that the Samaritans pronounced the name Iαβ?. Epiphanius ascribes the same pronunciation to an early Christian sect. Clement of Alexandria, still more exactly, pronounces 'Iαου? or 'Iαουα?, and Origen, 'Iα. 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. The Septuagint, and after it the New Testament, invariably render κ?ριος ("the Lord").