The earliest reference to the word hoodlum is in the December 15, 1866 Daily Alta California.
According to Herbert Asbury's book The Barbary Coast: An Informal History of the San Francisco Underworld (1933, A. A. Knopf, New York), the word originated in San Francisco from a particular street gang's call to unemployed Irishmen to "huddle 'em" (to beat up Chinese migrants), after which San Francisco newspapers took to calling street gangs "hoodlums".
hoodlum (plural hoodlums)
- “Frederick Bee History Project”, in (Please provide the title of the work), accessed October 4, 2014