Bring Your Own Chair. This is applicable in a situation where not enough seating will be available at a public event or event where many people want to sit, so visitors are advised to bring their own seating methods.
John: Movie night at my place, not enough chairs so BYOCh bitches!
Kelly: Hey, did you hear about John's party? The invite said BYOCh, there are gonna be a lot of people there!
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi