"of or involving very low temperatures," 1896, from cryo- "freezing" + -genic "having to do with production" (from PIE root *gene- "give birth, beget"). Cryogen "freezing mixture, that which produces cold" is attested from 1875. Related: Cryogenics (1958).
crux
cry
crybaby
crying
cryo-
cryogenic
crypt
cryptarchy
cryptic
crypto-
cryptogram