'humaneness' ultimately derives from the adjective 'humane,' which in turn comes from Latin 'humanus' meaning 'of man' or 'human'. The noun is formed by adding the English suffix '-ness' (denoting a state or quality) to 'humane'.

'humanus' (Latin) gave rise to Old French 'humain' and Middle English 'humaine'/'humayn'; the adjective 'humane' developed in Late Middle English/early Modern English, and the noun 'humaneness' was formed later by adding '-ness' to 'humane'.

Originally related to being 'of or pertaining to humans' (from Latin 'humanus'), the sense shifted toward 'compassionate, kind, and considerate' in later English; 'humaneness' now specifically denotes that compassionate quality.