Why is the ninth month called September?
c.1500, from Middle French faction (14c.) and directly from Latin factionem (nominative factio) "political party, class of persons," literally "a making or doing," from past participle stem of facere "to do" (see factitious). In ancient Rome, "one of the companies of contractors for the chariot races in the circus."
A group formed to seek some goal within a political party or a government. The term suggests quarrelsome dissent from the course pursued by the party or government majority: “His administration is moderate, but it contains a faction of extremists.”