factious adj.

c. 1500, from French faction (14c.) and directly from Latin factionem (nominative factio) "political party, of persons," literally "a making or doing," noun of action from past participle stem of facere "to do" (from PIE root *dhe- "to set, put"). In ancient Rome, originally "one of the four teams of contenders for the chariot races in the circus," distinguished by the color of their dress. Later "oligarchy, usurping faction, party seeking by irregular means to bring about a change in government."

A spirit of faction, which is apt to mingle its poison in the deliberations of all bodies of men, will often hurry the persons of whom they are composed into improprieties and excesses for which they would blush in a private capacity. [Hamilton, "The Federalist," No. 15]