1610s in reference to bowling, 1660s in reference to persons; past-participle adjective from bias (v.). The simple bias also formerly was used as an adjective.
Entries linking to biased
bias v.
"giving a bias to, causing to incline to one side," 1610s literal; 1620s figurative; from bias (n.). Compare French biasier. Related: Biased; biasing.
unbiased adj.
c. 1600, literal, in reference to throws at bowls, from un- (1) "not" + biased. Figurative sense of "impartial, unprejudiced" is recorded from 1640s.