The word 'undying' is a straightforward English compound formed from the native Germanic elements 'un-' and 'dying'. The prefix 'un-', with its ancient and persistent meaning of "not," directly negates the core concept of mortality and cessation conveyed by 'dying'. This logical construction creates a powerful adjective that literally means "not dying," which evolved to describe abstract qualities like fame, love, or devotion that are perceived as eternal and impervious to decay or death. Its formation follows a classic pattern in English for creating opposites and emphasizes permanence through the denial of an end.

Structure: un (not) + dying (ceasing to live) - un: A prefix of Germanic origin (Old English), meaning "not," serving a negating function. - dying: The present participle of the verb "die," from Old English dīegan, dēagan, of Germanic origin, indicating the act of ceasing to live.