'antislaveryism' originates from Modern English, specifically formed from the prefix 'anti-' (from Greek 'anti' meaning 'against') + the noun 'slavery' (from Medieval Latin 'sclavus' via Old French 'esclave', originally meaning 'Slav' as many Slavs were enslaved) + the suffix '-ism' (from Greek '-ismos' via Latin and French, used to form doctrines or systems).

'antislaveryism' developed as a compound and derivative in the 18th–19th centuries from the adjective/noun 'antislavery' (itself 'anti-' + 'slavery') with the addition of '-ism' to denote an ideology or movement; 'slavery' traces back through Middle English and Old French to Medieval Latin 'sclavus'.

Initially used to name opposition to slavery in historical contexts (notably 18th–19th century abolition movements), it retains that primary meaning and now refers generally to the doctrine or movement opposing slavery.