Cleaning something thoroughly by rubbing hard; searching intensely and carefully through something.
From Old Norse 'skúra' meaning to shower or wash. The word originally meant washing, then extended to mean any thorough, intense searching or cleaning action.
Medieval wool processors called 'scouring' the process of cleaning raw wool—they'd scrub it to remove grease and dirt, and the word stuck because scouring became the perfect word for intense, thorough cleaning of any kind.
Complete word intelligence in one call. Free tier — 50 lookups/day.