The compound "years-old" is a modern English construction that follows a Germanic pattern of combining two independent words to form a new descriptive term. The first element, "years," derives from the Old English "gēar," a term for a cycle of seasons, which has cognates across the Germanic language family. The second element, "old," comes from the Old English "eald," meaning aged or ancient. The hyphenated form "years-old" functions as a single unit, a postpositive adjective that attaches a specific numerical age to a noun, a logical and efficient grammatical development from its two foundational concepts of time and maturity.

This is a compound adjective formed from the plural noun 'years' and the adjective 'old'. 'Years' originates from Old English 'gēar', of Germanic origin, related to Dutch 'jaar' and German 'Jahr'. 'Old' originates from Old English 'ald, eald', of Germanic origin, related to Dutch 'oud' and German 'alt'.