Posterity is all the people who will come after us. For posterity, judged by posterity, leave it to posterity.
For posterity is the fixed phrase, used of recording or preserving something because future people will want it. Posterity will judge is what people say when the present verdict is against them. It also means descendants specifically, which is the older and narrower sense. Note that the Latin means those coming after, from post.
1nounposterityAll the people who will come after us.
“She kept all her letters for posterity, hoping her grandchildren would read them one day.”
posterity is future generations.
The post here is the one in postpone: after. Posterity is everyone who comes after us.
hooks ontopost
Latin posteritas comes from posterus, coming after, from post, after. Posterior, postpone and post-mortem come from the same after.
Latin
posteritas
Middle French
posterité
English, today
posterity
Built from
Late 14th century, from Middle French posterité, from Latin posteritas, from posterus (“following, coming after”), from post (“after”) (English post-).
Etymology from Wiktionary, CC BY-SA