'assignableness' originates in Modern English as the noun formed by adding the suffix '-ness' to 'assignable', where 'assignable' is 'assign' + '-able' (meaning 'capable of being').

'assign' originates from Latin 'assignare' (from 'ad-' + 'signare' meaning 'to mark, sign'). The verb entered Old French as 'assigner' and Middle English as 'assignen' or 'assigne'. From these forms came the adjective 'assignable' (with suffix '-able'), and the noun 'assignableness' was created by adding '-ness' to denote the quality or state.

Initially related to 'marking' or 'designating' (from Latin), it evolved toward the sense 'to allocate or allocate rights', and the modern derived noun means 'the quality of being capable of assignment or allocation.'