Suffix -arian as defined by Dictionary.com:
a suffix forming personal nouns corresponding to Latin adjectives ending in -ārius or English adjectives or nouns ending in -ary, (librarian; proletarian; Rotarian; seminarian; sexagenarian; veterinarian); subsequently productive in English with other Latinate stems, forming nouns denoting a person who supports, advocates, or practicesa doctrine, theory, or set of principles associated with the base word: authoritarian; establishmentarian; totalitarian; vegetarian.
Learn more about suffixes at Learn English.
Tip! Find list of most common suffixes and prefixes at Scholastic.