1520s, from Fr. biais
"slant, oblique," also figuratively, "expedient, means" (13c., in O.Fr. "sideways, askance, against the grain"), from O.Prov. biais
, with cognates in Old Catalan and Sardinian; possibly from V.L. *(e)bigassius
, from Gk. epikarsios
"athwart, crosswise, at an angle," from epi-
"upon" + karsios
"oblique," from PIE *krs-yo-
, from base *(s)ker-
"to cut." A pp. adjective that became a noun in Old French. Transferred sense of "predisposition, prejudice" is from 1570s.
"[A] technical term in the game of bowls, whence come all the later uses of the word." [OED]
The verb is from 1620s.