The compound adjective 'worn-down' is a relatively modern formation, emerging from the combination of the past participle 'worn' and the adverbial particle 'down'. The verb 'wear' itself has ancient Germanic roots, related to the concept of carrying or having on one's person, which evolved to include the gradual deterioration caused by use. The particle 'down' reinforces the directional metaphor of decline, moving from a higher to a lower state. Thus, the literal logic of the word paints a picture of something being gradually eroded or reduced through persistent use until it is in a diminished or exhausted condition.

Structure: worn (past participle of 'wear') + down (adverb/particle) - worn: From Old English werian (to wear, carry, have on). Past participle of the verb 'wear', indicating a state resulting from the action. - down: From Old English dūne, a shortened form of of dūne (from the hill). In this compound, it functions as an adverbial particle intensifying the sense of reduction or decline.