krypton (n.)

early 15c., cripte, "grotto, cavern," from Latin crypta "vault, cavern," from Greek krypte "a vault, crypt" (short for krypte kamara "hidden vault"), fem. of kryptos "hidden," verbal adjective from kryptein "to hide," which is of uncertain origin. Comparison has been made to Old Church Slavonic kryjo, kryti "to hide," Lithuanian kráuti "to pile up." Beekes writes that krypto "is formally and semantically reminiscent of [kalypto]; the verbs may have influenced each other." For this, see calypto-. But he adds, "However, since there is no good IE etymology, the word could be Pre-Greek." Meaning "underground burial vault or chapel in a church" is attested by 1789.

fictional substance in the "Superman" series, where it weakens the otherwise invulnerable hero, 1943; perhaps from elements of krypton (which is a gas) + meteorite.

gaseous element, 1898, from Greek xenon, neuter of xenos "foreign, strange" (from PIE root *ghos-ti- "stranger, guest, host"); coined by its co-discoverer, Scottish chemist Sir William Ramsay (1852-1916); compare krypton.