partiality n.

late 14c., "not whole or total, incomplete;" early 15c., "one-sided, biased, inclined to favor one party in a cause or one side of a question more than the other," also "pertaining to a selfish interest rather than to a common or larger good," from Old French parcial (14c., Modern French partial) and directly from Medieval Latin partialis "divisible, solitary, partial," from Latin pars (genitive partis) "a part, piece, a share, a division" (from PIE root *pere- (2) "to grant, allot").

Weakened sense of "favorably disposed" is from 1580s. Meaning "affecting a part only, not universal or general" is by 1640s.