"Pico de gallo” is a Mexican food, but probably more Cal-Mex than Tex-Mex. I pointed this dish out to the OED and supplied the 1962 citation below.


(Oxford English Dictionary)
pico de gallo, n.
Chiefly U.S.
[< Mexican Spanish pico de gallo a spicy Mexican relish, lit. ‘cockerel's beak’ < Spanish pico (see PICO- comb. form) + de DE prep. + gallo cockerel (1207; < classical Latin gallus: see GALLINE adj.).
It is uncertain why the Spanish phrase should be used in this sense; one suggested explanation is that this is due to the heat of the dish creating a painful sensation on the tongue, similar to being pecked by a bird.]

A Mexican salsa or salad, typically made with coarsely chopped tomatoes, onions, lemon juice, chillies, and coriander, and served as an accompaniment.

1962 Los Angeles Times E17/1 (heading) Pico de Gallo (Comb of the Rooster). 1970 Pomona (Calif.) Progress-Bull. 20 Feb. B3/5 Mexican fried rice, orange and cucumber salad called pico de gallo, and lemonade. 1991 Food & Wine Aug. 79/1 With the addition of cilantro, it is known as pico de gallo, a popular, all-purpose salsa.


23 February 1958, Independent Star-News (Pasadena, CA), Scene section (story about Guadalajara, Mexico), pg. 29:
Ponder this near-fatal event and its historical repercussions over a tequila chased by a “pico de gallo” (orange, jicama fruit and small, red and hot chile pepper) and the stern stuff of the Mexican Revolution will seem real.
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