as in, replaces "I swear" with something your sister might understand, but probably not your mom, and definitely not your grandma.
yo that flower that JimBob just got from the plug is LOUD. I mean we smoked 1/2 a joint and I was gassed bro and I dab 13 times a day. That shit is straight fire oml
OMLN means "Oh My Leo's Nose"
It is used as a replacement for common terms such as OMG and OML.
This is a reference to the game "A Way Out" and refers to Leo's huge and godlike nose.