2 Answers

Jah is often used to mean God- and therefore God's unconditional Love. In Rastafarian religion generally distinguished for asserting the doctrine that Haile Selassie I, the former and final Emperor of Ethiopia, is another incarnation of the Christian God, called Jah.[8] They see Haile Selassie I as Jah or Jah Rastafarian, who is the second coming of Jesus Christ onto the Earth.
So Basically it means God's unwavering Love.
It is also found in
The King James version of the bible shows us in Psalm 68: 1-4 WHO JAH IS, (The ONE that IS), which comes from JAHOVIAH, (Exodus 3: 14. Therefore JAH LOVE IS HIM. 1 John 4: 7-16.
"He who loves you."
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Jah is a short version of the name of true GOD and father of our lord Jesus Christ.
Hallelujah means Praise Jah you people

There is a hymn sung at Welsh rugby matches with gusto: Guide me o thou great Jehovah

You will find this name 4 times in the King James version of the bible.
Exodus 6V3, Psalm 83v18 Isaiah 12v2 & 26v4.

Jesus recommended 'Our father which art in heaven Ha-lowed be thy name.
but the churches would rather you did not know this.

Hope this clarifies