The compound adjective 'three-toed' is a transparent modern English formation. Its first element, 'three', descends from the Proto-Indo-European numeral trei-, which is the ancient source for the concept of the number across many language families, including Latin and Greek. The second element originates from Old English tā, referring to a digit of the foot, which combined with the suffix -ed creates an adjective meaning 'possessing toes'. The word's logic is purely descriptive, directly combining the count and the physical feature to specify a zoological characteristic, commonly used to distinguish certain species of sloths or woodpeckers.

Structure: three (number) + toed (having digits) - three: From Old English þrīe, of Germanic origin; related to Dutch drie and German drei, from an Indo-European root shared by Latin tres and Greek treis. Functions as a numerical root. - toed: From the noun toe (Old English tā, of Germanic origin) + the adjectival suffix -ed, meaning 'having or provided with'. Functions as the descriptive base.