It would've had to been if it references the Black and Tans. That said, it's part of a long tradition of Irish resistance songs, most famous of which are The Wearing of the Green and The Rising of the Moon, both of which date back to the failed rising of 1798.
And here's another one commemorating the Irish victory at Glenmalure in 1580. The lyrics weren't written until the Nineteenth Century, but the tune was purportedly used by the troops of Fiach McHugh O'Byrne during the Second Desmond Rebellion.
Thanks for sharing this gem. Seems like there are many of them. Atleast we can properly date them it's pity that same is not case with the ancient Indian chants.
Oldest available Indian or probably Indo-European music is found in Samveda which is inarguably best preserved 'musical' literature of ancient world thanks to the detailed and dedicated method with which it was propagated. We had about thousand chating styles but only a few could survive.
Samveda chants are essentially 'religious' so we can't know how folk/popular music used to be in those days.