I think you should think think about there are two setsets of Chinese charaters. In Hongkong, Taiwan and some Chinese communities in the UK, US, traditional Chinese charaters are still used; whereas people on mainland China use simplified Chinese charaters. Here there is a traditional Chinese word, 後, which may mean "behind" and the word 后 means "queen". In simplified Chinese, 後 is replaced by 后 and hence Chinese in China may not know 後 and think it is an obsolescent word but Chinese in other regions are still using it.