A childhood belief about swearing

When I was in primary school, we used to do this little rhyme where we said, "Silence in the courtyard, silence in the street, the biggest twit in England is just about to speak - starting from now." One time I said this little rhyme, but instead of saying 'twit' I said 'twat' because I thought they meant the same thing and were equally rude. Twit isn't a very rude word, so I assumed that twat wasn't either. So the little boy, Tim, who had spoken and been crowned the biggest twat in England, by me, went mooching to the teacher and went "She said I was the biggest twat." and I got severely told off. *blush*