Irish jig tune. The "Larry O'Gaff" title for the tune comes from a nonsensical stage-Irish song whose words are only rarely reported (they can be found in a folk version in Creighton's Songs and Ballads from Nova Scotia), and it appears the melody normally was used as an instrumental piece. The tune/song is firmly ensconced in the late minstrel/early vaudeville stage. It is usually associated with Northeastern players in the United States.
Larry O'Gaff was a brave boy for marching, His instep was larege--but his income was small; So he set up, one day, as a soldier of fortune-- The meaning of which is--no fortune at all.