1580s, "act as an umpire, mediate, decide, determine, give an authoritative decision," from Latin arbitratus, past participle of arbitrari "be of an opinion, give a decision," from arbiter "a judge, umpire, mediator" (see arbiter). Meaning "act as an arbitrator" is from 1610s. Related: Arbitrated; arbitrating; arbitrable (1530s). The earlier verb form was arbitren "decide a dispute by arbitration" (early 15c.).