>There is a story about Chile - the term gringo may have started there. Seems a number of Irish immigrated there around 1845 and would sing songs about Ireland (Erie) and the line "green grows the grass" was heard over and over so they were called gringos. I have seen this reference in several books but who knows?

I heard the same legend about cowboys singing a similar song in Mexico...
Sounds like an urban.. um... rural legend.