Noun
Chathamite (plural Chathamites)
(historical) A supporter of William Pitt, 1st Earl of Chatham (1708–1778), British Whig politician.
After a decade of factional chaos, with distinct " Grenvillite ", " Bedfordite ", " Rockinghamite ", and " Chathamite " factions successively in power, and all referring to themselves as "Whigs", a new system emerged with two separate opposition groups. Source: Internet