One of the popular songs the St Patricks Brigade would sing was Green grow the rushes O .
Which some people say is how the word Gringo Came about the Mexicans would hear the Irish singing it and the first 2 words would sound like Gringo.
Here is a video of the song The guy playing the pipes is a old child hood friend that I use to swap stamps with back in the day, I was talking to him a year ago when the group was on the north America tour and he still collects.
http://www.youtube.com/watch?v=90bE4VvJBTE