‘Hallelujah’ is a combination of two Hebrew words, ‘Hallelu’ and ‘Jah’.

‘Jah’ is pronounced ‘Yah’.  It is an abbreviated version  – Yhwh, a common name for God.  Unfortunately, history does not share how Yhwh was pronounced, but it is pronounced as Yahweh today (‘Jehovah’ is also a popular, but incorrect pronounciation).  Yhwh is usually rendered “the LORD” in Bible translations.

‘Hallelu’ is another form of the Hebrew word ‘Hallal’, which means ‘praise’.  However, ‘Hallelu’ is the second person plural imperative conjugation of this word.  This means it’s not a personal call but instead a request for others to praise Yah –  i.e. “praise Yah all you people”.

References of Hallelujah in the bible:

https://www.biblegateway.com/quicksearch/?quicksearch=hallelujah&qs_version=NIV&oq=Halelujah