Fag Marks
Blood residue left in someone underpants. Typically the result of anal sex
"Excuse me grocer, do you sell this particular brand of detergent? It is the only kind that can get out fag marks."
"Fag Marks?"
"Blood."
"Get the hell out of my store."
"Fag Marks?"
"Blood."
"Get the hell out of my store."