'antislavery' originates from Modern English, formed by combining the prefix 'anti-' (from Greek 'anti' meaning 'against') with 'slavery' (from Old French and Latin roots).

'antislavery' developed in the 18th–19th centuries as the phrase 'anti-slavery' (anti- + slavery) began to be used widely in political discourse; over time the hyphenated form often became the single word 'antislavery'. 'Slavery' itself ultimately comes from Medieval Latin 'sclavus' (meaning 'Slav', used to mean 'slave'), via Old French and Middle English.

Initially used to denote opposition to slavery (often referring to a political movement), it has retained that core meaning and is still used to describe people, arguments, or movements opposed to slavery.