Frankie McPhillip tells his mother he travelled to her house via O'Connell Street. In 1922, the year the movie is set, O'Connell Street was still offically called Sackville Street, but the Irish Home Rule Party had unsuccessfully attempted to change it to "O'Connell Street" prior to this and this name was commonly used by nationalist Dubliners.
The surname Gallagher is pronounced "Galligger" by characters, however, in Ireland the name is always pronounced "Gallaher."