Watson, is an artificial intelligent system initially created to see if it could beat the best of the Jeopardy! Contestants, which included Ken Jennings. Long story short, Watson eventually did beat Ken Jennings in a game of Jeopardy!
However, when Watson would communicate with humans, it sounded very artificial. Eric Brown, someone who helped design Watson, decided it would be best if he added the entire 'Urban Dictionary' to Watson's vocabulary so it could pick up and use slang terms as most humans do. Unfortunately, Watson picked up all the sexual terms and swear words, and began using those nonchalantly.
In order to bring Watson back down to a PG-13 rating, technicians had to design a swear filter for Watson so it wouldn't swear uncontrollably!