antecedent

n. /ˌæn.t̬əˈsiː.dənt/ C1

前情；先例；祖先

A thing or event that existed before another and influenced it.

仙境例句

The Dodo said the Caucus-race had an antecedent: a race its grandfather once ran in circles.

渡渡鸟说，团团转赛跑早有先例：它爷爷当年就绕着圈跑过。