Other forms: scoured, scouring, scours
To scour is to search a place thoroughly, or to scrub it clean. Scour the area, scour the pan, scoured the records.
The searching sense implies covering every part — police scour an area, researchers scour records — and it is the commoner one in writing. The scrubbing sense is the older, and a scourer is the abrasive pad. In geology, scour is what fast water does to a riverbed, which is a real hazard for bridge foundations. Note scouring pad.
Middle English scouren came from Middle Dutch schuren, probably from Old French escurer, from Latin excurare, to clean off. Cure and curate come from the same caring.
Proto-Indo-European
*kʷeys- — to heed
Medieval Latin
scūrō
Old French
escurer
Middle Dutch
scuren
Middle English
scouren — to polish, scour; to clean; to beat, whip
English, today
scour
Built from
From Middle English scouren (“to polish, scour; to clean; to beat, whip”), from Middle Dutch scuren, schuren (“to clean; to polish”) or Middle Low German schǖren, of uncertain origin but probably from Old French escurer, from Medieval Latin scūrō, escūrō, excūrō (“to clean off”), from ex- (“thoroughly”) + cūrō (“to arrange, see to, take care of”), from cūra (“care, concern”) (from Proto-Indo-European kʷeys- (“to heed”)) + -ō. The word is cognate with Danish skure, Middle High German schüren, schiuren (modern German scheuern (“to scour, scrub; to chafe”)), Norwegian skura (“to scrub”), Swedish skura, Catalan escurar.
Etymology from Wiktionary, CC BY-SA