"judicial or legal order," c.1500, from Middle French mandat (15c.) and directly from Latin mandatum "commission, command, order," noun use of neuter past participle of mandare "to order, commit to one's charge," literally "to give into one's hand," probably from manus "hand" (see manual) + dare "to give" (see date (n.1)). Political sense of "approval supposedly conferred by voters to the policies or slogans advocated by winners of an election" is from 1796. League of Nations sense is from 1919.
1620s, "to command," from mandate (n.). Meaning "to delegate authority, permit to act on behalf of a group" is from 1958; used earlier in the context of the League of Nations, "to authorize a power to control a certain territory for some specified purpose" (1919). Related: Mandated; mandating.
A command or an expression of a desire, especially by a group of voters for a political program. Politicians elected in landslide victories often claim that their policies have received a mandate from the voters.