When did the yarmulke become Jewish?

Last Friday night someone at shul asked if I knew anything about the origin of yarmulke. He said that he found an interesting source and wondered if I could confirm or refute it. Since then I have been searching for answers. The problem is, there is no exact answer. The origin of the word itself is uncertain and could be the subject of a full article. The more I search, the more uncertain the answer becomes. In my next Librarian's Lobby I will explore some of the story. As a librarian the search is almost as interesting as the answer.