'peaceableness' originates from English, specifically formed from the adjective 'peaceable' plus the suffix '-ness', where 'peace' ultimately comes from Old French 'pais' (from Latin 'pax, pacis') meaning 'peace'.

'peaceableness' developed from Middle English formations based on Old French and Latin roots: Old French 'pais' > Middle English 'pece/peys' (peace) combined with the adjective-forming element (yielding 'peaceable') and then the noun-forming suffix '-ness' to produce 'peaceableness'.

Initially it referred simply to 'the state or condition of being peaceable'; over time the word's use has remained largely consistent, though it is somewhat formal or literary in modern usage.