Semantics is the study of the meaning of words. As you may well know, the meaning of words changes all the time. By looking at this change we can learn a lot about history and even about the human psyche.

Pejoration: from bad to good and back again.

If the attitude of a word changes to the negative, we call this pejoration. This mainly happens because people love to use euphemisms (nice words for ugly things). The problem is, that by using a euphemism too often its original positive meaning will eventually be lost and only the negative connotation remains. Here are some examples: