not-so-young

The compound adjective "not-so-young" is a modern English phrasal construction, not a single inherited lexical unit. It follows a transparent and logical syntactic pattern common in Germanic languages: negation ("not") + a degree qualifier ("so") + a core adjective ("young"). Each component maintains its original etymological function. "Young" derives from Proto-Germanic jungaz, ultimately from the Proto-Indo-European root yeu- meaning "vital force, youthful vigor." The words "not" and "so" have equally ancient Germanic lineages. The phrase as a whole is a euphemistic or humorous lexicalization, creating a single conceptual unit that politely or ironically denotes middle age or beyond by literally stating the subject is "not as young" as they once were, demonstrating how analytic syntax can fossilize into a compound modifier.

Structure: not (negation) + so (degree) + young (age) not: From Old English 'nāwiht', 'nōht', meaning "nothing, not at all." A negative particle. so: From Old English 'swā', meaning "in this way, to such an extent." An adverb of degree or manner. young: From Old English 'geong', meaning "young, youthful." An adjective describing age.