'American-leaning' originates from English, specifically the word 'American' combined with the present participle 'leaning', where 'American' meant 'of or relating to America' and 'lean' meant 'to incline or bend toward'.

'American' comes from the proper name 'America' (named after Amerigo Vespucci) and entered English as an adjective meaning 'relating to America'; 'leaning' derives from Old English 'hlinian'/'hlynan' (to incline), later Middle English 'lenen/lenen' and modern 'lean' + '-ing', and the compound form 'American-leaning' developed by joining the adjective and participle to express inclination toward America.

Initially, 'American' simply identified relation to the place or people called America, and 'lean' meant 'to incline'; over time the compound 'American-leaning' came to mean 'inclined toward American ideas, policies, or styles'—a figurative extension of physical inclination into preference or bias.