"The quality of not growing old; the non-appearance of the signs of age", Early 18th cent.; earliest use found in Phillips's New World of Words. From post-classical Latin agerasia from Hellenistic Greek ἀγηρασία eternal youth (Galen) from ancient Greek ἀ- + γῆρας old age + -ία.[agerasia etymology, agerasia origin, 英语词源]