Green’s Dictionary of Slang

1. a Mexican, esp. one considered lower class or of mixed blood.

1966		M. Rumaker Exit 3 and Other Stories 39: Don’t give me any lip, chico.
1978		Maledicta II:1+2 (Summer/Winter) 154: Chico A familiar diminutive applied to males of Spanish-American descent, especially in professional sports [...] Since the sixties, ‘Chico’ is dropping out of usage [...] and no player has been called ‘Chico’ on the big-league level since 1973.
1978		(con. WWII) T. Sanchez Hollywoodland (1981) n.p.: Chico, you think we don’t know what you are up to in the Barrio?
1980		E. Folb Runnin’ Down Some Lines 56: Terms like Chico, Felipe and Cholo used [with] playful or affectionate overtones; other times they were used in an openly hostile and derisive way.
1991		C. Hiaasen Native Tongue 194: Don’t push it, chico.
2012		M. MacLean ‘Just Like Maria’ in ThugLit Oct. [ebook] ‘Who was that chico you were with?’.

2. a Puerto Rican, also a term of address.

1967		P. Thomas Down These Mean Streets (1970) 17: ‘Come on, chicos,’ I said. ‘Let’s get this game going.’.
2000		P. Beatty Tuff 53: Listen, joko, Give me a pound of papas, Chico.

3. a Cuban.

1986		C. Hiaasen Tourist Season (1987) 14: I’ve got a question for you, chico.
1993		C. Hiaasen Strip Tease 135: Hey, chico, we’re in the middle of a recession.

4. a Filipino.

1944

P. Kendall Dict. Service Sl. n.p.: Chico . . . Philippino.