In the early 16th century, Scottish poets Walter Kennedy and William Dunbar faced off for a bout of flighting, which is basically their version of a rap battle in which Kennedy called Dunbar a shit, but wit, which means he's shit, but without any wit. And it wasn't until the end of the 18 hundreds that people turned shit into an interjection. Considering that people were self censoring damned during that same period was considered pretty bad