In the late 1920s, there was a temporary break-up of Innisfails' junior football team in Balgriffin, and as a result it was decided to form a team in Portmarnock. At that time, Portmarnock would have been what is now called 'Old Portmarnock'. The population was sparse and if a team lost a few players it found it very difficult to survive. The team was named St. Marnocks after a contemporary of St. Patrick, who first introduced Christianity to Portmarnock. The team wore a black jersey with an amber sash, the colours of which were inspired by the crest of the Jameson family, of whiskey fame, who lived locally.