gainsay (v.)

"contradict, deny, dispute," c. 1300, literally "say against," from gain- (Old English gegn- "against;" see again) + say (v.). In Middle English it translates Latin contradicere. "Solitary survival of a once common prefix" [Weekley]. It also figured in such now-obsolete compounds as gain-taking "taking back again," gainclap "a counterstroke," gainbuy "redeem," Gaincoming "Second Advent," and gainstand "to oppose." Related: Gainsaid; gainsaying.