'anti-' originates from Greek, specifically the prefix 'anti-' meaning 'against', and 'extremism' originates from the adjective 'extreme' (from Latin 'extremus') with the suffix '-ism' forming a noun indicating a practice or ideology.

'extreme' passed from Latin 'extremus' into Old French and Middle English as 'extreme'; the abstract noun 'extremism' was formed in English by adding the suffix '-ism' (via French/Latin patterns) in the 19th century. The compound 'anti-extremism' arose in the 20th century as a political term combining 'anti-' + 'extremism'.

Initially, compounds with 'anti-' plus political nouns typically meant simple opposition to a specified doctrine; over time, 'anti-extremism' has broadened to cover not only oppositional belief but also organized policies, prevention programs, and legal measures aimed at combating radicalization.