@Alyx Oh, I didn't even realize that similarity! I thought *chan in Japanese was related to Martial Arts. But indeed, it's like the German *chen.
And being the supreme procrastinator that I am, I immediately had to go on a search on similarities between the German and Japanese language and was amazed about the results. I did realize that many people see Germany and Japan as having similar cultures, but I never realized the linguistic overlaps, e.g. see
https://www.sljfaq.org/afaq/german.html