Nut is a common English word with multiple meanings:
1. A hard-shelled fruit or seed (e.g. walnut, almond)
2. A small metal piece used with a bolt
3. Slang for someone who is crazy or eccentric
4. (vulgar slang) Testicles
5. Enthusiast or fan (e.g. "movie nut")
6. The head (e.g. "off one's nut")
7. In music, the part of a string instrument that supports the strings