'avowableness' originates from Modern English, specifically from the adjective 'avowable', where the root 'avow' meant 'to declare or acknowledge openly'.

'avowableness' was formed by adding the adjective-forming suffix '-able' to the verb 'avow' to create 'avowable', and then the nominal suffix '-ness' produced 'avowableness'. The verb 'avow' entered English via Old French 'avouer' (to acknowledge), ultimately deriving from Latin roots related to declaring or acknowledging.

Initially it meant 'able to be declared or acknowledged', and over time this developed into the noun form meaning 'the quality of being avowable', a sense that is retained in modern usage.