"the refuse matter which passes through sewers," 1818, probably from the apparent base of sewer (n.1) + -age. There was a verb sew "to drain, to draw off water," attested from late 15c., but by 19c. it seems to have survived only in provincial dialect, and OED writes, "It was prob. framed without any knowledge of the verb as having been actually used." Compare sewerage.
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.