The song makes reference to a crucial date in the Irish history : find it out and take notes on where and what happened that year.
Use the dictionaries in this blog to find the pronounciation of the word GUN in British English and compare it to the pronounciation of the word in the song. What is the main difference?
http://en.wikipedia.org/wiki/Irish_War_of_Independence
Dictionary link:
http://ilikethisbloggymuch.blogspot.com.es/search/label/Project%20task%3A%20English%20dictionaries.