Here's some more on Skin the Goat, obtained from the National Graves Association in Dublin.

"Skin the Goat" was the nickname of James Fitzharris (1833-1910), driver of the "growler" used by the killers. Born in Camolin, Co. Wexford, Fitzharris, lived in Lime Street. Being a cab driver, he had access to the comings and goings of Dublin Castle and supplied the assassins with vital information. His nickname is probably derived from an old wake custom, feannadh an phocháin, "skinning the goat": an ancient country ritual in which a piece of skin from a corpse was used as a love charm. In more sophisticated Dublin, the term had come to mean a simple-minded person and it was said of Fitzharris that no one dared call him "Skin the Goat" to his face; though "Skin" was, apparently, quite acceptable!                                                                         
   He certainly "stood up for his principles". Despite being offered £10,000, he refused to turn informer. At his first trial, for murder, he was acquitted, but at a second trial was found guilty of conspiracy and sentenced to penal servitude for life. He was released from Maryborough (now Portlaoise) Prison on 23 August 1899. He is buried in a substantial grave in Glasnevin. In 1938, the National Graves Association erected a memorial and in 1968 a bronze plaque was added, giving the names of his five executed co-conspirators. He too is commemorated in song, "James Fitzharris, the Invincible",

I never told what I saw there,
They might as well ask my old grey mare,
Ten thousand pounds would be my fare,
If I'd give information.