As always, “rational” is subjective. Pinyin, the transliteration scheme in use in this post (in use in the PRC since the 50s or so), is necessarily full of trad

As always, “rational” is subjective. Pinyin, the transliteration scheme in use in this post (in use in the PRC since the 50s or so), is necessarily full of trade-offs. Ch is already needed to represent a sound which is much closer to the English “Ch”, as in Chen. But then there is this other sound, which sounds superficially like Ch to a non-native speaker, but actually is quite different (and if you mix them up, you might not be understood by a native speaker). What letter do you use for that? Originally people used Ts, as in Tsingtao the beer, named for the city on the coast (but that wasn’t perfect either, because the sound also has very little in common with T). Then in the 50s Pinyin came along and it was changed to Q, so Qingdao (the final consonant was changed too). Btw this change in transliteration schemes is why Peking Duck is still a thing: even though the city’s name is now spelled Beijing, the old spelling of Peking lives on in the name of the dish (and a few other places).