The "Green Grow the Lilacs" story has been around a long time, but doesn't hold much water, for all the reasons cited above by people who apparently know far more than I do. The word actually comes from an archaic form of "griego" - which did mean Greek, but also any stranger (as in, "It's all Greek to me"). I remember in my Latin American Studies days at the University of Texas hearing a paper delivered on this very topic at a conference. One point made was that the idea of "gringo" as a misheard song lyric would have been very popular with those who wanted to portray Mexicans - and in particular mestizos - dimwitted. After all, it might have been reasoned, they couldn't even hear song lyrics correctly.

We, of course, like the theory because we like singing and are thus innocent from galloping ethnocentrism.

Dan