Football hooliganism or soccer hooliganism constitutes barbaric behaviour perpetrated by spectators at association football events. Football hooliganism normally involves conflict between gangs, in English known as football firms (derived from the British slang for a criminal gang), formed to intimidate and attack supporters of other teams. Other English-language terms commonly used in connection with hooligan firms include "army", "boys", "bods", "casuals", and "crew". Certain clubs have long-standing rivalries with other clubs and hooliganism associated with matches between them (sometimes called local derbies) is likely to be more severe.