Yes, the flat cap, aka paddy cap, newsboy cap, Gatsby cap and other names. has been borrowed just yesterday by the hip-hop scene and and the porno scene.  But it has been around a long time, and in other settings it sends a message of tweedy “establishment” and “older guy.”  It has been basic country head-gear in Britain for a couple of centuries, where you’d find it on English gentry, Irish horse trainers and Scottish golfers.  Immigrants brought it to the U.S.