from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A gaily decorated cap, usually with a number of loose peaks tipped with bells, formerly worn by court jesters and clowns.
- n. See dunce cap.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A cap, usually brightly coloured with bells and tassels, as worn by a court jester or fool.
fool ("jester, entertainer") + cap (Wiktionary)