'anti-Americanism' is formed from the prefix 'anti-' (from Greek anti- 'against'), the adjective 'American' (from 'America', named after the explorer Amerigo Vespucci), and the suffix '-ism' (from Greek/Latin indicating a doctrine or practice).

'anti-' (Greek) + 'America' (from the name Amerigo Vespucci via Latin and French) produced 'anti-American' in English; adding the noun-forming suffix '-ism' (from Greek/Latin through Old French) gave 'anti-Americanism' in modern English usage, appearing in the 19th–20th centuries as political discourse around U.S. influence grew.

Originally it described opposition to specific American policies or influence; over time its use broadened to include cultural prejudice, general hostility toward Americans, and organized political movements opposing U.S. power.