lens: [17] The Latin word for a ‘lentil’ was lēns; and when 17th-century scientists wanted a term for a round biconvex (lentil-shaped) piece of glass, they needed to look no further than lens. English lentil [13] itself comes via Old French from Latin lenticula, a diminutive form of lēns. => lentil[lens etymology, lens origin, 英语词源]