'applicableness' originates from Late Middle English, formed from the adjective 'applicable' plus the noun-forming suffix '-ness'. 'applicable' ultimately comes from Latin 'applicabilis', from 'applicare', where the prefix 'ad-' (seen in the form 'ap-') meant 'to' and the root 'plicare' meant 'to fold or join.'

'applicableness' developed by adding the native English suffix '-ness' to the adjective 'applicable' (Middle English and Old French influences). 'applicable' itself passed into English via Old French from Latin 'applicabilis' (from 'applicare'), and over time the compound became the English noun 'applicableness'.

Initially related to the literal sense of 'being attached or applied' (from Latin ideas of 'joining' or 'applying'), the emphasis shifted to the abstract sense of 'suitability' or 'relevance', which is the primary meaning today.