“Perdurable” comes to us from late Middle English via Old French. It derives from the late Latin “perdurabilis,” which stems from Latin “perdurare,” meaning “endure.” You’d be hard-pressed to find anything more perdurable than xenon-124: At 18 sextillion years, it has the longest half-life of any material that’s been directly measured in a lab. For some perspective, 18 sextillion years is about 1 trillion times the age of the universe.