The word hallelujah is a transliteration of two Hebrew words: “הָלַל” (hallelu) and “יָהּ” (ah). Write down those two Hebrew words using the closest equivalent letters we have in English, and you end up with that strange and beautiful word hallelujah or alleluia.
The first Hebrew word hallelu means “let us praise.” And the second word is Yah, which is the short form of Yahweh—the very specific, personal name of the God of Israel.
Yahweh has its origin in the name God revealed to distinguish Himself from all other gods. In Exodus chapter 3, when God speaks to Moses for the first time and calls him to bring His people out of slavery in Egypt, Moses says, “If the Israelites ask me Your name, what should I say?” And God responds, “I AM WHO I AM.”
The name Yahweh is built out of the Hebrew word for “I AM.” So it’s a name that is intended to make us marvel at the self-sustaining, eternally existing, utterly transcendent nature of this God, the true and living God who is quite unlike any other pretender to the throne. When the name Yahweh appears in the Old Testament, it’s often translated “LORD” in capital letters in our English translations, to mark it out from the more generic word “God.”
So hallelujah means “Let us praise Yah.” Let us join together in worshiping and praising this God—Yahweh—and no other.