5 letters · 8 points in Scrabble
originFrom Middle English rewayn, from Anglo-Norman rewain, from an Old Northern French variant of Old French regain (“an increase”), from re- + gaigner (“to till, win”). The alternative forms represent replacement of unanalysable final /ən/ with the more tractable suffixes -et, -ing; roughing presumably relies on a lost pronunciation of rough as /ˈɹaʊ/.
Etymology from Wiktionary, CC BY-SA 3.0