"scheiße" means shit;
"kopf" means head.
Each word by itself makes sense in German; the combination of these two words does not make sense.
English speakers put these two words together to make a new word, "
shithead". This works in English. Doing so in German, however, does not
work.
Just ask any German-speaking person: they'll tell you "scheißekopf" makes no sense in German.
To
avoid sounding like a dummkopf,
don't
use the contrived and inaccurate term, scheißekopf.