Some think that the original was butt, based on that word having been used to refer to a person’s buttocks since the 17th century, and that buck was a euphemism. Well, not really, but there are several theories. Looking into the origin of which word to put before naked and you will find more schools of thought than you would at a joint conference of Digital Humanities and American Studies. SFW: Suitable For Woods Origin of 'Buck Naked' vs.