1) Abbreviation for "On God" meaning to heavily agree to something, and
show that agreement by mentioning the life of God.
2) Misspelling of "OMG" which is an abbreviation for Oh My God/Gosh/
etc.
1)
P1: "My favorite part about the party was how hyper the DJ was"
P2: "ONG
DUDE"
2)
P1: "ONG I JUST GOT TOLD VERY BAD NEWS ABOUT MY
PARENTS"
P2: "You misspelled OMG, dumbass."
P1: "Why does that matter...?"