or love-bite. Named after the biblical mark placed on Cain after he killed his brother... 'cause when you've got it, everyone knows what went down last night.
"Dude, did Jack screw that chick he was with last night?"
"I dunno, but you saw the Mark of Cain he's been flaunting."
"Hey, I'm digging the Mark of Cain."
"Yeah. I think my gf's a vampire, actually."