A native German-speaker would probably have also given you a double-take. The word would be "Scheißkopf," and though it would definitely be understood that you were trying to be insulting, that isn't a fixed expression in German, just as my quickly consulting my German->English dictionary and calling you a "duck-squeezer" or a "currant-crapper" wouldn't make much sense to you (an "Entenklemmer" is a tightwad, while a "Korinthenkacker" is an anal-retentive, bureaucratic, or niggling person), though I might still get beaten up for my trouble.
Regards,
I knew what I was saying, trust me. I know enough German.
I could have said ‘’arseloche’’ too, (a-hole in German).