rare More fully "white satin flower". Either of two plants of the genus Lunaria, the annual L. annua and the perennial L. rediviva, which have flattened seed pods with a silvery sheen on the inner membrane. Compare "honesty". Also called satin, satin flower.
2More fully "white satin moth". The satin moth, Leucoma salicis.
Late 16th century; earliest use found in John Gerard (c1545–1612), herbalist. From white + satin, probably with allusion to colour and sheen and to smoothness.