When I was in Skopelos, a local mentioned that this expression was used to someone who was heavily snogging his girlfriend. He explained that it meant if you carry on like that you’ll soon be kissing her backside. I’m going over some old notes in a set of notebooks that I have made during my travels to Greece. It obviously is an abbreviation for κώλο but I’ve never come across this expression since. Is it in common colloquial use like στον κώλο σου?