the wikipedia article on Chinese numerology says in the same paragraph both that the number 4 has been unlucky since ancient times in China AND that the idea that 4 is unlucky is a recent development in China. impressive!
@soph_sol that study is interesting though, if totally unhelpful 😆
@Satsuma there are a couple of citations in that part of the article. One is to an academic study on whether more Cantonese-speaking people die on days with 4 in the number (no) and although it talks about the cultural association, it doesn't actually mention whether it's an association that's recent or ancient. The other is to a random personal website with no particular authority, which asserts an ancient origin.
so..... they have useful citations for neither, lol.