I didn’t learn the word ‘shart’ until I was in my fifties. Thought it was pretty nifty slang.
Fifties for me, too. I don't think the term existed when I was fifteen.
I learned it from my cousin who was in his forties. My mother warned me about him. At least I'm not layin' this on old Schwartz like Ralphie did. He's been through enough as I recall hearing over the phone. :/