A saeculum is a length of time roughly equal to the potential lifetime of a person or, equivalently, of the complete renewal of a human population.[1] The term was first used by the Etruscans. Originally it meant the period of time from the moment that something happened (for example the founding of a city) until the point in time that all people who had lived at the first moment had died. At that point a new saeculum would start. According to legend, the gods had allotted a certain number of saecula to every people or civilization; the Etruscans themselves, for example, had been given ten saecula.[2]
Source: Saeculum – Wikipedia
Tim B.
https://blog.archive.org/2019/09/26/what-happens-when-everyone-who-experienced-an-event-is-gone/
Tim B.
https://en.wiktionary.org/wiki/saeculum#Latin
“the amount of time between an occurrence and the death of the final person who was alive at, or witness to, that occurrence”