Jehovah
Jehovah [EBD]
the special and significant name (not merely an appellative title such as Lord [adonai]) by which God revealed himself to the ancient Hebrews (Ex. 6:2, 3). This name, the Tetragrammaton of the Greeks, was held by the later Jews to be so sacred that it was never pronounced except by the high priest on the great Day of Atonement, when he entered into the most holy place. Whenever this name occurred in the sacred books they pronounced it, as they still do, "Adonai" (i.e., Lord), thus using another word in its stead. The Massorets gave to it the vowel-points appropriate to this word. This Jewish practice was founded on a false interpretation of Lev. 24:16. The meaning of the word appears from Ex. 3:14 to be "the unchanging, eternal, self-existent God," the "I am that I am," a convenant-keeping God. (Comp. Mal. 3:6; Hos. 12:5; Rev. 1:4, 8.)
The Hebrew name "Jehovah" is generally translated in the Authorized Version (and the Revised Version has not departed from this rule) by the word LORD printed in small capitals, to distinguish it from the rendering of the Hebrew Adonai and the Greek Kurios, which are also rendered Lord, but printed in the usual type. The Hebrew word is translated "Jehovah" only in Ex. 6:3; Ps. 83:18; Isa. 12:2; 26:4, and in the compound names mentioned below.
It is worthy of notice that this name is never used in the LXX., the Samaritan Pentateuch, the Apocrypha, or in the New Testament. It is found, however, on the "Moabite stone" (q.v.), and consequently it must have been in the days of Mesba so commonly pronounced by the Hebrews as to be familiar to their heathen neighbours.
Jehovah [NAVE]
JEHOVAHUsed in the KJV occasionally, and the ASV 1901 as the norm, Jehovah is an artificial form for the personal name of God, which is likely pronounced "Yahweh" (i.e., translated, "the LORD"). See: I Am Who I Am.
JEHOVAH [SMITH]
(I am; the eternal living one). The Scripture appellation of the supreme Being, usually interpreted as signifying self-derived and permanent existence. The Jews scrupulously avoided every mention of this name of God, substituting in its stead one or other of the words with whose proper vowel-points it may happen to be written. This custom, which had its origin in reverence, was founded upon an erroneous rendering of (Leviticus 24:16) from which it was inferred that the mere utterance of the name constituted a capital offence. According to Jewish tradition, it was pronounced but once a year, by the high priest on the day of atonement when he entered the holy of holies; but on this point there is some doubt. When Moses received his commission to be the deliverer of Israel, the Almighty, who appeared in the burning bush, communicated to him the name which he should give as the credentials of his mission: "And God said unto Moses, "I AM THAT I AM (ehyea asher ehyeh); and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you." That this passage is intended to indicate the etymology of Jehovah, as understood by the Hebrews, no one has ventured to doubt. While Elohim exhibits God displayed in his power as the creator and governor of the physical universe, the name Jehovah designates his nature as he stands in relation to man, as the only almighty, true, personal, holy Being, a spirit and "the father of spirits," (Numbers 16:22) comp. John 4:24 Who revealed himself to his people, made a covenant with them, and became their lawgiver, and to whom all honor and worship are due.Also see definition of "Jehovah" in Word Study