Is it ensure, insure, or assure?
1630s, "hidden, occult, mystical," from Late Latin crypticus, from Greek kryptikos "fit for concealing," from kryptos "hidden" (see crypt). Meaning "mysterious, enigmatic" is recorded from 1920. Related: Cryptically.
cryptic cryp·tic (krĭp'tĭk)
Hidden or concealed.
Tending to conceal or camouflage, as the coloring of an animal.