It comes from the word leap, with the idea being that you jumped on someone -> leaped someone -> lepped someone
Areas used: Ireland and Northern Ireland
Lisa: Yeah, but we didn't lep-lep or anything
Ruth: Why, do you not think he's leppable?
Lisa: Yeah, he's leppable, but I've just met him. Soon though!
Ruth: Lucky thing - I'm dying for a lep-lep