'premillennialist' is formed from the prefix 'pre-' (from Latin 'prae', meaning 'before'), the adjective 'millennial' (from Latin 'millennium', from 'mille' meaning 'thousand' + 'annus' meaning 'year'), and the agent suffix '-ist' (from Greek/Latin '-istēs' / '-ista', meaning 'one who').

'millennium' entered English from Late Latin 'millennium' (literally 'thousand years'); the adjective 'millennial' was formed from that root. The compound 'premillennial' (pre- + millennial) arose in theological discussions, and the noun form 'premillennialist' (one who holds that view) was later formed by adding the agentive suffix '-ist', becoming established in English usage during 19th-century theological debates.

Originally the components referred simply to 'before' + 'a thousand years'; over time the combined term came to denote the specific theological position that Christ will return prior to a literal thousand-year reign, and 'premillennialist' specifically denotes an adherent of that position.