Wordorigins.org

It is commonly believed that our so-called “four-letter words” are all Anglo-Saxon in origin, dating back to the earliest days of our language. In most cases, this is a false assumption. Most of our modern swear words are much more recent than the Old English era. Shit, however, does go back to an Old English root, *scítan . It has cognates in most of the other Germanic languages and shares a common Germanic root with modern equivalents like the modern German scheissen.