Ruffian, thug, hoodlum, hooligan, and lout. They all generally refer to a troublemaker, a violent man. But I wonder if there are any nuances of meaning between them. For example, we usually say "football hooligans," but why not "football hoodlums"?
"Ruffian" and "thug" are more or less synonyms, although "ruffian" is an old-fashioned term; however, both words are used for discribing criminal behaviour of the worst kind, that is murder and banditism, whereas the crimes associated with either hoodlums, looligans, and louts are not as bad, although occasionally the individuals so called can be guilty of murder; on the whole those latter are just noisy and violent lawbreakers.
I think that the reason football hoodlums is not used is because the gangs in which are found hoodlums do not associate with football events but with the life of the streets, and that of various entertainment places, such as drinking places for instance.