The expression “Hallelujah,” which occurs 24 times in the Hebrew Scriptures, literally is a command
to a number of people to “praise Jah” - a poetic shortened form of 'Jehovah', the name of the Most High God. (Ex 15:1, 2)
"The word halal is the source of `Hallelujah,' a Hebrew expression of `praise' to God which has been taken over into virtually every language of mankind. The Hebrew `Hallelujah' is generally translated [falsely], `Praise the Lord!' The Hebrew is more technically [more honestly] translated `Let us praise Yah,' the term `Yah' being a shortened form of `Yahweh,' the unique Israelite name for God." - p. 301, -
Nelson's Expository Dictionary of the Old Testament, Unger and White, Thomas Nelson Publ., 1980.
"Hallelujah - Praise ye Jehovah - frequently rendered [falsely] `Praise Ye the Lord" - p. 276. "Jah - a shortened form of `Jehovah,'" - p. 322,
Today's Bible Dictionary, Bethany House Publishers, 1982.
"HALLELUJAH ... 'praise ye Jehovah'; allelouia .... In the NT ['Hallelujah'] is found as part of the song of the heavenly host (Rev. 19:1 ff)." - p. 1323, Vol. 2,
The International Standard Bible Encyclopaedia, Eerdmans Publ., 1984 printing.
"hallelujah: (Heb., hillel, he praises; Jah, form of Yahweh-Jehovah....) Literally, Praise ye Yahweh." - p. 320,
An Encyclopedia of Religion, Ferm (editor), 1945 ed.
"HALLELUJAH - HALLELOUIA [in NT Greek] signifies `Praise ye Jah.' .... In the N.T. it is found in Rev. 19:1, 3, 4, 6, as the keynote in the song of the great multitude in Heaven. Alleluia, without the initial H, is a misspelling." - p. 520, W. E. Vine,
An Expository Dictionary of New Testament Words, Thomas Nelson, Inc., Publishers, 1980.
"ALLELUIA, the Greek form (Revelation 19:1, 3, 4, 6) of the Hebrew Hallelujah = Praise ye Jehovah, which begins or ends several of the psalms (106, 111, 112, 113, etc.)." –
Easton's Bible Dictionary, Thomas Nelson Publ., 1897.
The NT Greek text does have the initial `H' sound. The "misspelling" is in certain English translations (e.g., KJV) which drop the beginning `H' sound: "Alleluia"! However, most respected modern translations do have "Hallelujah" in Rev. 19 (e.g., NIV, NASB, RSV, NRSV, ASV, REB, MLB, Mo, and Barclay).
"Hallelujah....is derived from halal, which means to praise, and Jah, which is the name of God .... here in this chapter [Rev. 19] the original Hebrew form transliterated into Greek, is retained." - p. 169, Vol. 2, William Barclay,
The Revelation of John, Revised Edition, The Daily Study Bible Series, Westminster Press, 1976.
"Alleluia, so written in Rev. 19:6, foll., or more properly Hallelujah, Praise ye Jehovah ...." - p. 31. "Jah (Jehovah), the abbreviated form of Jehovah ... The identity of Jah and Jehovah is strongly marked in two passages of Isaiah - 12:2; 26:4." - p. 276,
Smith's Bible Dictionary, William Smith, Hendrickson Publ.
"Trust ye in Jehovah for ever; for in Jehovah ['Heb. JAH' - ASV f. n.], even Jehovah [YHWH], is an everlasting rock." - Is. 26:4, ASV.
Yes, Jah is equivalent to Jehovah. Two different forms of the very same PERSONAL NAME of God. (This is likely equivalent to the way Greek manuscripts often abbreviated "God" [Qeos, 'theos'] as QS. If so, Jah would still be pronounced "Jehovah" or "Yahweh".)
Psalm 68:4,
King James Version - "Sing unto God, sing praises to his name; extol him...by his name JAH ['Jehovah' - ASV; LB]..."
Of course, the Gentile manuscript copyists of later centuries probably did not know that "Abi-JAH" ("The Father is Jehovah"), "Eli-JAH," ("God is Jehovah"), etc. are transliterations that actually use the shortened form of God's personal name ("Jah") and certainly didn't know that "Hallelujah" (Rev. 19:1, 3, 4, 6) is really Hebrew for "Praise Jah" or they would have surely changed them all also. However, the inspired Jewish Christians who actually wrote the original NT manuscripts certainly knew that writing or proclaiming aloud "Hallelu JAH!" (whether in Hebrew characters or Greek characters) was writing (or proclaiming aloud) God's personal name. If the Jewish Christian and Apostle John had left God's name out of the NT originally, he surely would not have then used "Hallelu JAH!" in four places in Revelation 19, for he knew exactly what it truly said: "Praise ye Jehovah"! Only the Hebrew-ignorant Gentile "Christian" copyists would be fooled by "Hallelujah" exactly as they were when they removed and changed the Divine Name in the Septuagint about the same time).
Also see:
Hallelujah / Jah - The Removal of God's Name and Why "Hallelujah" Remained
http://defendingjehovahswitnesses.blogspot.com/2012/09/hallelujah-jah-removal-of-gods-name-and.html
More Information Concerning This Can Be Found In the Following Articles:
Jah
http://wol.jw.org/en/wol/d/r1/lp-e/1200002288?q=Hallelujah&p=par
HALLELUJAH (Watchtower Online Library INDEX)
http://wol.jw.org/en/wol/d/r1/lp-e/1200272571
HALLELUJAH (Insight on the Scriptures, Volume 1)
http://wol.jw.org/en/wol/d/r1/lp-e/1200001830