A scavenger, broadly, looks through discarded material seeking items that are of use to him. He is therefore ‘inspecting’ the material in order to select the useful from the useless.

Further info’ on etymology:

Alteration of Middle English scauager, schavager, official charged with street maintenance, from Anglo-Norman scawager, toll collector, from scawage, a tax on the goods of foreign merchants, from Flemish scauwen, to look at, show. Show: Old English scEawian to look, look at, see; akin to Old High German scouwOn to look, look at, and probably to Latin cavEre to be on one's guard.
Date: 12th century.