million-year-old

The compound adjective "million-year-old" is a modern English construction built from three distinct and ancient roots. "Million" originates from the Latin concept of a "great thousand," while "year" descends from a Proto-Indo-European term for a cycle of seasons. "Old" stems from an Indo-European root meaning "to grow," implying the state achieved through the passage of time. The compound's logic is transparently literal, combining a vast numerical quantifier with a standard unit of time and an adjective of age to describe something of immense geological or cosmological antiquity.

Structure: million (numerical unit) + year (time period) + old (aged) - million: From Italian milione, from Latin mille (thousand) + the augmentative suffix -one. Functions as a numerical quantifier. - year: From Old English gēar, from Proto-Germanic jērą, from Proto-Indo-European yeh₁r- ("year, season"). Functions as a unit of time. - old: From Old English eald, from Proto-Germanic aldaz, from Proto-Indo-European h₂el- ("to grow, nourish"). Functions as an adjective describing age or duration.