Etymology
From Middle English scavage, schevage, schewage, from Anglo-Norman escavage, escauwage, alteration of earlier escauvinghe (“scavage”), from Middle English shewing, schewing (“inspection, examination, show”), from Old English sċēawung (“a looking at, seeing, contemplation, consideration, respect, regard, reconnoitering, surveying, inspection, examination, scrutiny, a spectacle, show, appearance, pretence, a showing, exhibiting, manifestation, toll on exposure of goods”), equivalent to show + -ing. Doublet of shewage.
Definitions & examples from Wiktionary (CC BY-SA 3.0).