the compound adjective 'worn-out' is a relatively modern formation, emerging from the combination of the past participle 'worn' and the adverbial particle 'out'. the verb 'wear' itself has deep germanic roots, tracing back to proto-germanic wazjaną and ultimately to the pie root wes- (to clothe). the particle 'out' derives from pie úd (up, out, away). the logic of the compound is transparent: an object is 'worn' (diminished by use) to the point of being 'out' (completely used up, exhausted). this literal sense of a depleted object was then metaphorically extended to describe a person's state of extreme fatigue, where one's energy is completely used up.

Structure: worn (past participle of 'wear') + out (adverb/particle) 'worn' originates from old english 'werian' (to wear, carry, have on) and functions as the past participle of the verb 'wear'. 'out' originates from old english 'ūt' (out, outside, forth) and functions as an adverbial particle indicating a state of completion or exhaustion.