"small, narrow opening, crevice," mid-15c., possibly from a diminutive of Old French cran, cren "a notch, a hole, a cut, fissure" (14c.), from crener "to notch, split," from Medieval Latin crenare, which is possibly from Latin cernere "to separate, sift" (from PIE root *krei- "to sieve"). Compare Old French crene "notched." But OED casts doubt on this derivation. Related: Crannied (mid-15c.).