'Americanly' originates from English, specifically the adjective 'American' + the adverbial suffix '-ly', where '-ly' meant 'in the manner of' (from Old English '-līċ'/'-lice').

'Americanly' formed by adding the productive English suffix '-ly' to 'American'. 'American' itself comes from the place-name 'America', named after the explorer 'Amerigo' (Latinized to 'Americus'), which produced the adjective 'American' in the late 16th century.

Initially related simply to 'of or pertaining to America' as an adjective; with the suffix '-ly' it evolved into an adverb meaning 'in an American manner' or 'in the way typical of Americans'.