1392, from M.L. retina, probably from V.L. (tunica) *retina, lit. "net-like tunic," on resemblance to the network of blood vessels at the back of the eye, and ult. from L. rete "net." The V.L. phrase may be Gerard of Cremona's 12c. translation of Ar. (tabaqa) sabakiva "netlike layer," itself a translation of Gk. amphiblestroeides (khiton).