'attachableness' originates from Modern English, specifically formed by adding the suffix '-ness' to 'attachable' (itself from 'attach' + '-able'), where 'attach' means 'to fasten or join' and '-ness' denotes a state or quality.

'attach' came into English via Middle English from Old French (such as 'atachier'/'attachier'), and 'attachable' developed by adding the adjectival suffix '-able'; later English formations added '-ness' to form 'attachableness'.

Initially the root 'attach' primarily meant 'to fasten' or 'to fix in place'; over time the derived noun 'attachableness' has been used to denote the more general capability or suitability for attachment rather than only physical fastening.