This is not a Chinese abbreviation.
It is a Chinese transliteration of Spanish abbreviation.
Manchester City, abbreviated in Chinese, is called "Blue Moon" because Manchester City fans often sing the classic old song "Blue Moon" to cheer for the team. At home games, the beautiful song "Blue Moon" always echoes in Etihad Stadium.
The fans of Manchester City Expeditionary Force also brought this song to every away game. It can be said that there is this classic "Blue Moon" where there is a Manchester City game.