'assailability' originates from Modern English, formed from the adjective 'assailable' plus the noun-forming suffix '-ity'; 'assailable' derives from the verb 'assail.'

'assail' comes from Old French 'assaillir' (to attack), which in turn derives from Vulgar Latin *'assalīre' (from Latin prefix 'ad-' meaning 'to, toward' + 'salīre' meaning 'to leap'); through Middle English the forms developed into modern 'assail' and then 'assailable' and 'assailability'.

Initially associated with the physical action 'to attack' (to leap upon or assault); over time it expanded to include figurative senses (to criticize or challenge), and the noun now denotes the state of being open to either physical or verbal attack.