'proclined' originates from Latin, specifically the verb 'proclinare', where 'pro-' meant 'forward' and 'clinare' meant 'to lean'.

'proclined' came into English via Late Latin/Medieval Latin forms related to 'proclinare' and through Middle English adaptations (e.g. forms like 'proclinen'), eventually producing the modern English verb 'procline' and its past/p.p. 'proclined'.

Initially it meant 'to bend or lean forward' in a literal, physical sense, but over time it also acquired the broader sense of 'to be inclined or disposed toward' (a tendency or attitude).