Why is the ninth month called September?
late 14c., from Old French bargaignier (12c., Modern French barguigner) "to haggle over the price," perhaps from Frankish *borganjan "to lend" or some other Germanic source, ultimately from Proto-Germanic *borgan (cf. Old High German borgen; Old English borgian, source of borrow). Another suggestion is that the French word comes from Late Latin barca "a barge," because it "carries goods to and fro." There are difficulties with both suggestions. Related: Bargained; bargaining.
mid-14c., "business transaction or agreement," also "that which is acquired by bargaining," from Old French bargaine, from bargaignier (see bargain (v.)). Meaning "article priced for special sale" is from 1899. A bargain basement (1899) originally was a basement floor in a store where bargains were displayed.