Hello everyone! In this piece of news you can read the expression "以「菱角」敲打他的頭", an expression I often heard when I was a kid (except that we use the verb hang1 or kok1, not haau1 敲 in speech), but I haven't heard of it for many years. What nostalgia! I think the Northern equivalent is 敲爆栗 (interestingly enough, it seems to be 栗暴 in 《水滸》). The closest thing I can think of in English is "noogie" in American English, although 敲爆栗 is a single strike, and doesn't involve the action of rubbing. Now I wonder what do you say in your dialect for this action? Any other fruits besides chestnut and water caltrop?