"erectile organ of female mammals," 1610s, coined in Modern Latin from Late Greek kleitoris, a diminutive, but the exact sense intended by the coiners is uncertain. Perhaps from Greek kleiein "to sheathe," also "to shut," in reference to its being covered by the labia minora. The related Greek noun form kleis has a second meaning of "a key, a latch or hook (to close a door);" see close, v., and compare slot, n.2.Alternatively, perhaps related to Greek kleitys, a variant of klitys "side of a hill," itself related to klinein "to slope," from the same root as climax (see lean, v.), and with a sense of "little hill." Some ancient medical sources give a supposed Greek verb kleitoriazein "to touch or titillate lasciviously, to tickle" (compare German slang der Kitzler "clitoris," literally "the tickler"), but the verb is likely from the anatomy in this case.The anatomist Mateo Renaldo Colombo (1516-1559), professor at Padua, claimed to have discovered it ("De re anatomica," 1559, p. 243). He called it amor Veneris, vel dulcedo "the love or sweetness of Venus." It had been known earlier to women.