c.1175, "power of discernment," from O.N. skil "distinction, discernment," related to skilja (v.) "distinguish, separate," from P.Gmc. *skaljo- "divide, separate" (cf. M.L.G. schillen "to differ;" M.L.G., M.Du. schele "difference;" see
shell). Sense of "ability, cleverness" first recorded c.1300.