The compound adjective 'used-up' is a relatively modern formation, emerging from the earlier phrasal verb 'to use up', meaning to consume completely. The literal sense of 'use' (from Latin uti) combined with the completive sense of the particle 'up' (from Old English, implying finality or exhaustion of a resource) created a vivid metaphor. This concrete meaning of total consumption was then figuratively extended to describe a person whose energy or vitality has been entirely depleted, as if it were a resource that had been spent. Thus, the term logically bridges the physical act of finishing a material supply and the abstract state of human fatigue.

Structure: used (past participle) + up (adverbial particle) 'used' originates from Old French 'user', from Latin 'uti' (to use, employ), functioning as a past participle. 'up' originates from Old English 'up', 'upp', an adverb and preposition meaning 'to a higher position', functioning as an adverbial particle completing the phrasal verb.