1680s, with reference to leaves, petals, teeth, etc., "falling off at a certain stage of existence," from Latin deciduus "that which falls down," from decidere "to fall off, fall down," from de "down" (see de-) + combining form of cadere "to fall," from PIE root *kad- "to fall." Of trees and bushes, "losing foliage every year" (opposed to evergreen), from 1778. The Latin adjective was used of shooting stars and testicles, but it seems not to have been used of trees or leaves (the phenomenon in Italy seems to be restricted to the mountain regions). Related: Deciduousness.