“Chūgoku” or “Chuugoku” (中国), often translated as “China”, was the derogatory nickname for the Touhou Project charater, Hong Meiling. It used to be more prominent in the 2000s, but it slowly died out as Meiling's character became more fleshed-out as the series progressed.

In Touhou Koumakyou, Meiling has the title of “Chinese Girl” (華人小娘, Kajinko Musume). However, at the time, Meiling was arguably irrelevant and people just didn't have a good reason to respect her character.¹⁾ Then on April 3, 2003, an anonymous 2channel user brought up how their friend group would specifically call Meiling, “Chūgoku” (中国) or “China”, and this nickname somehow managed to catch on.²⁾

Some people did fight the nickname, but ZUN incidentally approved of the nickname's use in January 2004 while answering a question in the “Gensou Keijiban” board, saying “China is fine” (中国で良いですよ).³⁾⁴⁾ This was revisited at the “Dawn of Touhou” (東方の夜明け) event at Meiji University on October 31, 2004 where he was asked if the nickname was “dark history”, but ZUN acted confused.⁵⁾⁶⁾

While early games did joke that characters forgot her name, Meiling would became a genuinely developed character that the fan nickname was phased out. The definitive turning point was 2009 after Meiling had become a main character in Touhou Hisoutensoku, with personality details like borrowing a Tengu-authored manga from Remilia and being surprised that heaven actually knew of Chinese literature.

• In the past, there used to be urban legend that her name came from a dispute about how her name should be read⁷⁾ and someone went “Why don't we call her China and call it a day?”
• There's a rumor that this nickname allegedly started because the trial version of Touhou Koumakyou didn't list their names, but this can be easily debunked with “ver 0.08” gameplay footage.⁸⁾
• In the original Touhou Soccer fan game, Meiling is called “Jack” (ジャック, Jakku), referencing the protagonist of Super Chinese, localized as Kung-Fu Heroes or Ninja Boy.
• Another factor that contributed to the nickname's decline is that more Chinese characters were added in Touhou Project, so it would be really awkward if people kept using it despite the fact.

• Pad Chief
• Touhou Character Names (ZH)