From Middle English crany, crani, apparently a diminutive of *cran (+ -y), from Old French cran, cren, a derivative of crener, from Medieval Latin crenō ("split"), from Vulgar Latin ("split, break"), of obscure origin.
Despite a spurious use in Pliny, connection to Latin crēna is doubtful. Instead, probably of Germanic or Celtic origin. Compare Old High German chrinna ("notch, groove, crevice"), Alemannic German Krinne ("small crack, channel, groove"), Low German karn ("notch, groove, crevice, cranny"), Old Irish ara-chrinin ("to perish, decay").