sleeve

袖 is composed of the radical of 衣 (clothing) and 由 (reason). 由 depicts oil droplets congealing into fat, with the original meaning being oil or fat, and by extension conveys the idea of smoothness or slipperiness; thus 袖 conveys the idea of the part of a garment from the shoulder to the wrist—the smoothest portion of the entire garment, otherwise the arm could not slide through—and means sleeve.