Middle English word reward comes from French garder, Old French warder ((Old Northern French, Anglo-Norman).), French reconqueste, Old French re- (Re- (again; once more).), Old French guarder (To look at. To protect; to guard.)

Detailed word origin of reward

Dictionary entry	Language	Definition
garder	French (fra)	(pronominal) to be careful (de faire not to do). (transitive) to guard. (transitive) to keep; to retain; to store; to save.
warder	Old French (fro)	(Old Northern French, Anglo-Norman).
reconqueste	French (fra)
re-	Old French (fro)	Re- (again; once more).
guarder	Old French (fro)	To look at. To protect; to guard.
rewarder	Old French (fro)
reward	Anglo-Norman (xno)
reguarder	Old French (fro)	To look at. To watch.
regard	Old French (fro)	Look; observance; watching (act, instance of looking at). Payment. Reward.
rewarde	Middle English (enm)

Words with the same origin as reward