'aquilinity' originates from Latin, specifically from the adjective 'aquilinus' (from 'aquila'), where 'aquila' meant 'eagle'.

'aquilinus' passed into Late Latin and then into English via the adjective 'aquiline' (meaning 'eagle-like'); 'aquilinity' was later formed in English as a noun denoting the quality of being aquiline.

Initially the Latin root referred directly to the bird 'eagle'; over time it evolved into an adjective meaning 'eagle-like' and then into the noun 'aquilinity' meaning 'the state or quality of being eagle-like (especially in facial profile)'.