Scavenger
mid 16th century: alteration of earlier scavager, from Anglo-Norman French scawager, from Old Northern French escauwer ‘inspect’, from Flemish scauwen ‘to show’. The term originally denoted an officer who collected scavage, a toll on foreign merchants' goods offered for sale in a town, later a person who kept the streets clean.
wiktionary
Originally from Middle English scavager, from Anglo-Norman scawageour(“one who had to do with scavage, inspector, tax collector”), from Old Northern French *scawage, escauwage(“scavage”), Old French *scavage, escavage, alteration of escauvinghe (compare Medieval Latin scewinga, sceawinga), from Old Dutch scauwōn(“to inspect, to examinate, to look at”). Usually reinterpreted/re-analysed today as scavenge (which was originally a backformation from this word) + -er. Compare Old English sċēawung(“a showing, spectacle, examination, inspection, toll on exposure of goods”) and Dutch schouwing(“inspection”). More at show.
etymonline
scavenger (n.)
1540s, originally "person hired to remove refuse from streets," from Middle English scawageour (late 14c.), London official in charge of collecting tax on goods sold by foreign merchants, from Anglo-French scawager, from scawage "toll or duty on goods offered for sale in one's precinct" (c. 1400), from Old North French escauwage "inspection," from a Germanic source (compare Old High German scouwon, Old English sceawian "to look at, inspect;" see show (v.)).
It has come to be regarded as an agent noun in -er, but the verb is a late back-formation from the noun. With unetymological -n- (c. 1500) as in harbinger, passenger, messenger, etc. Extended to animals 1590s. Scavenger hunt is attested from 1937.
