I once made a terrible error. I don't remember who it was, or where it was... But I was talking to someone about an incident I had in which I was "jipped." You know, "ripped off." He levels his stare and says, "not cool man, I'm part Gypsie." At which point it dawned on me that "jipped" is actually "gypped."
I just said, "sorry man, I had no idea the root of that word. I didn't mean anything." I felt pretty stupid about it.