Hallelujah means to praise God. It is considered
the highest praise by some Chistians, and
litterally means "Let us praise God".
Hallelujah is also sometimes considered halleluyah, because thats how its
pronounced, and because God's names are "Jahova" or short form "Jah", or "Yahwah", or a short form "Yah", which composes the ending of the word.