'Arianism' originates from the proper name 'Arius' (Latin 'Arius'), the 4th-century Alexandrian presbyter whose teachings gave the movement its name, combined with the suffix '-ism' (from Greek '-ismos' via Latin and French) meaning 'doctrine' or 'system of belief'.

'Arianism' passed into English from Medieval Latin 'Arianismus' (and Old French 'arianisme'), the term used to denote the teachings of Arius; it entered modern English as 'Arianism'.

Initially it referred specifically to the doctrines taught by Arius in the early 4th century; over time it has come to denote the broader movement, related theologies denying Christ's coequal divinity, and more generally the heretical position contrasted with Nicene orthodoxy.