"parti-colored, variegated with spots of different colors," late 14c. (early 14c. in surnames), as if it were the past participle of a verb form of the Middle English noun pie "magpie" (see pie (n.2)), in reference to the bird's black and white plumage. Earliest use is in reference to the pyed freres, an order of friars who wore black and white. Also in pied piper (1845, in Browning's poem based on the German legend; used allusively by 1939).