Contrary to some things that have
been posted here, the US did not wear green
coats, or green
uniforms, during the Mexican American
War, so that
explanation for the origin of this word is bogus.
But the term is indeed related to American
soldiers who invaded Mexico during the Mexican-American
war. It actually came from the lines of what
a song that
was very popular with American
See the example.
A popular American
song during that time--one
sung by many American
troops as they marched--contained the repeated
"Oh, the ash and the oak and the willow tree,
grows the grass on the infantry"
Being members of the infantry, the second line was sung with particular fervor. "Green
grows" sounded like "gringoes" to the non-English-speaking
Mexicans, so they used that term to refer
to all of the American