Claim: The word gringo came from Mexicans' overhearing American
soldiers sing the song "Green Grow the Lilacs" during the
Mexican-American War. Origins: The rather improbable saga of the
origins of the word "gringo" has it that the term began during
the Mexican-American War (1846-48), when Mexicans supposedly
overheard American soldiers continually singing either "Green
Grow the Lilacs" or "Green Grow the Rushes, O" (a song based
upon a Robert Burns poem). Purportedly, the Spanish-speaking
Mexicans thereupon began derisively referring to the Americans
as "green grows" (rendered phonetically in Spanish as gringos),
which soon became a pejorative Spanish-language term for
"foreigners" (particularly Americans). Other versions of this
etymological legend attribute the singing to Irish Legion
volunteers serving in Simon Bolivar's army during Venezuela's
war for independence from Spain in the early 19th century,
"cowboys in south Texas," or American troops attempting to track
down Pancho Villa in Mexico in 1916-17.