The phrase "supporters du CO" refers to the supporters of the Castres Olympique (CO), a French rugby union club. "Supporters du CO" is French for "[supporters of the CO](javascript:void(0))." Castres Olympique is a well- known rugby team with a passionate fan base, and "supporters du CO" designates those who support or follow this team closely. The term "du" is a French preposition meaning "of the," linking the supporters with the club. The "CO" stands for Castres Olympique, which is often abbreviated as CO in France. This phrase is commonly used in contexts related to the fans, events, and culture around the rugby club.