I've known the song by Patrick Galvin a long time, but I don't understand the verse
So they buried him down in yon green garden
With union men on every side
They swore they would form a mighty union
That James Connolly's name might be filled with pride

because I read that Connolly and most of the other executed leaders of the 1916 Easter Rising were buried in a mass grave. There does not seem to have been any re-interment? The bodies were covered in quicklime so that they would decompose more quickly.