'pro-American' originates from two elements: the prefix 'pro-' (from Latin 'pro') and 'American' (from 'America', named after the Italian explorer Amerigo Vespucci). Here, 'pro-' meant 'for' and 'American' refers to 'of or relating to America.'

'pro-' as a productive prefix in English (from Latin 'pro') combined with adjectives denoting national affiliation (such as 'American', formed from 'America') to create compounds like 'pro-American'; hyphenation and solid forms have varied in modern English usage, with the hyphenated form 'pro-American' common for clarity.

Initially this formation literally meant 'for America' (i.e., 'for the American side'); over time it has come to conventionally mean 'supportive of the United States, its government, policies, or culture' in political and cultural contexts.