Pseudo german. A compound of "Scheisse"(=shit) and "Kopf"(=head) that forms the literal translation of the popular english insult "shithead". Doesn't really work in german, because "Scheiss-" is an equivalent of "fucking ...", so "Scheisskopf" would mean something like "fucking head".
"Scheissekopf" isn't an alternative, it doesn't work at all.
The boys looked up some words in the dictionary and came up with "scheissekopf".
German for any tea biscuit or cookie. Though "Keks" was originally intended to be a plural form of "Kek", it has become a singular form (proper plural is now "Kekse").
Invented by biscuit-manufacturer Bahlsen when he first introduced his Leibnitz biscuits around 1900. When people couldn't pronounce the english word "cakes", Bahlsen made up "Keks".