"I used to be a banker, but I lost interest." is a:

1. A pun is word play that exploits multiple meanings of a term. 2. "Interest" can mean curiosity or the money a bank pays. 3. The joke works because both meanings fit. 4. So the line is a pun. **Why not the others:** A simile compares with "like", a refrain repeats a line, and a euphemism softens a word. _Source: Wikipedia, "Pun", section "introduction" (revision 1379861948)_