'detachability' originates from English, formed from the verb 'detach' + the suffix '-ability'; 'detach' ultimately comes from Old French 'détacher', where the prefix 'des-' (from Latin 'dis-') meant 'apart, away' and the root related to 'attach' meant 'to fasten or join'.

'detach' changed from Old French 'détacher' (or earlier 'destachier') into Middle English forms such as 'detachen' and later the modern English verb 'detach'; the abstract noun was created in Modern English by adding the suffix '-ability' (from Latin '-abilitas').

Initially it referred to the action 'to separate or unfasten'; over time the derived noun came to denote the property or quality 'the capability of being detached', which is its current meaning.