1620s, "council or body of representatives," from French syndicat (15c.), from syndic "representative of a corporation" (see syndic) + -at (see -ate (1)). Meaning "combination of capitalists or companies to carry out some commercial undertaking" first occurs 1865. Publishing sense of "association of publishers for purchasing articles, etc., for simultaneous publication in a number of newspapers" is from 1889. As a synonym for "organized crime, the Mob" it is recorded from 1929.
1889, "form into a syndicate," from syndicate (n.). Meaning "sell for simultaneous publication" is from 1889. Earlier it meant "to judge, censure" (1610s), from Medieval Latin syndicatus, past participle of syndicare. Related: Syndicated; syndicating.