The word 'unused' is a straightforward English compound formed by attaching the native Germanic negative prefix 'un-' to the past participle 'used'. The core concept of 'use' traces back to the Latin verb uti, meaning to employ, enjoy, or make practical application of something. Over centuries, 'use' evolved in English to cover both the act of employing something and the state of being accustomed to it. Therefore, 'unused' logically inherits a dual sense: the literal state of not having been employed, and the figurative state of not being practiced or accustomed, preserving a clear and direct semantic link from its constituent parts.

Structure: un (not) + used (employed) - un: A prefix of Germanic origin (Old English, Old High German, Old Norse) meaning "not," serving a negating function. - used: The past participle of the verb 'use', from Old French user, from Latin usare 'to use', frequentative of uti 'to use, employ, enjoy'. It functions as the core lexical element describing the state of employment or familiarity.