"not partial, not favoring one over another," 1590s, from assimilated form of in- (1) "not, opposite of" + partial. First recorded use is in "Richard II." Related: Impartially.

What country did impartial originate?

Borrowed from Middle French impartial. See im- +‎ partial.

What Latin word does impartial come from?

Word History: Today's Good Word is an assimilated form of in- "not, opposite of" + partial "biased, prejudiced". This is yet another word English borrowed from French, which inherited it from Latin partialis "divisible, partial", the adjective accompanying pars, partis "part, piece".