clitoris.

From post-classical New Latin clītoris (16th century), from Koine Greek κλειτορίς (kleitorís), probably from Ancient Greek κλείω (kleíō, “to sheathe, shut”), in reference to it being covered by the labia minora. The related noun form κλείς (kleís) has a second meaning of "a key, a latch or hook (to close a door)." Wooden pegs were the original keys; a connection also revealed in Latin clavis (“nail”) and claudere (“to shut”) (see close). Some medical sources give a supposed Greek verb κλειτοριάζω (kleitoriázō, “touch or titillate lasciviously, tickle”) literally "to be inclined (toward pleasure)" (compare German Kitzler (“clitoris”, literally “tickler”), related to Greek κλειτύς (kleitús, “shut, closed”), a variant of κλιτύς (klitús, “hillside”), related to κλίνω (klínō, “to slope”), from the same root as κλῖμαξ (klîmax, “ladder”). But many sources take κλειτορίς (kleitorís) literally as Ancient Greek "little hill".