Cockney rhyming slang for Muslim
Derived from the name of the popular British DJ- Fatboy 'Slim'. The word 'slim' being taken from the second syllable of the word Muslim and coded to be spoken simply as 'Fatboy'
''we should probably take the next train because theres some dodgy looking Fatboys just got on to that carriage''
''theres no chance of getting a beer in this country, this place is run by Fatboys & its against their rules''