The term “Jah” in on Jah is the short form of the Hebrew word for God. Therefore, the slang “on Jah” is equivalent to the English “on God”.
“On God” is something you would say when you swear something is true or you praise something/someone.
The Rastafaris would often use the term “Jah” for God, or when referring to Haile Selassie, who some claimed was the incarnation of God.
Today the slang phrase is popular thanks to an internet meme that refers to late hip-hop artist XXXTentacion as God called “Jah”, due to his original name being Jahseh Onfroy.
“Jah” is the short form of Hebrew acronym “YHWH”, the four letters that make up the tetragrammaton, the personal name of God used by the Israelites. It is part of the phrase “hallelujah” meaning “praise God”.
After the death of XXXTentacion in 2018, fans found that his original name, Jahseh, could be shortened to “Jah”, indicating that he is God. The idea that he is God, or “Jah” spread to the internet in 2019, particularly in the form of memes often including his mugshot.
In March 2019, an image macro was uploaded to ME.ME including the mugshot of XXXTentacion, and the bar for armor from Minecraft. As an unfortunate twist, the top item box for the armor, usually reserved for the headpiece, contains a bullet. The dark meme is captioned “on Jah” and is a reference to the way the artist was killed.
Apart from the memes, the phrase is just another way of saying “on God”, particularly for XXXTentacion fans that perceived him as one, and were devastated by his death.
- Urban Dictionary – Jah