1630s, "to turn aside or ward off" the blow of a weapon (transitive), from French parez! (a word which would have been heard often in fencing lessons), imperative of parer "ward off," from Italian parare "to ward or defend (a blow)" (see para- (2)). Related: Parried; parrying. Non-fencing use is from 1718. The noun, "an act of warding off or turning aside," is by 1705, from the verb.
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.