That last line is a refereance to a poem Plunkett wrote, and you'll find it in this thread

His full name was actually Joseph Mary Plunkett, and that's the name used with his poems, but when he signed the Proclamation in 1916 - which was why he was one of those picked out to be shot - he left out the Mary, I believe, because he didn't feel it respectful to include it in what was effectively a declaration of war.

As well as poems he wrote a couple of good songs - one about Foot and Mouth that I posted in the Mudcat earlier this year, and another called The Planets which I put a tune to, because so far as I know it didn't have one.