Jah can be rendered as Jah or Yah and is
short for Jehovah or Yahweh (or Yehowah) in a poetic sort of way. This shortened form of the divine name appeared 50 times in the Hebrew scriptures, 26 as Jah or Yah, and 24 as Hallelujah. The word “Hallelujah” is Greek for a Hebrew phrase. The phrase translates as a literal command to a group of
people to “praise Jah,” or “Yah.”
Literally, "Praise Ye Jehovah."