Why is the ninth month called September?
early 15c., "grotto, cavern," from Latin crypta "vault, cavern," from Greek krypte (short for krypte kamara "hidden vault"), fem. of kryptos "hidden," verbal adjective from kryptein "to hide," from PIE *krau- "to conceal, hide" (cf. Old Church Slavonic kryjo, kryti "to hide"). Meaning "underground burial vault or chapel in a church" first attested 1789.
A small pit, recess, or glandular cavity in the body.