Mexican vs wetback

Mexican and wetback both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mexican	Yes	Yes	No	No
wetback	Yes	No	No	No

As nouns, wetback is a hyponym of Mexican; that is, wetback is a word with a more specific, narrower meaning than Mexican:

Other hyponyms of Mexican include Taracahitian, Chicano, greaser, taco, Mexican-American, Mexicano.

Mexican (noun)	wetback (noun)
a native or inhabitant of Mexico	(ethnic slur) offensive term for a person of Mexican descent

Mexican (adjective)	wetback (adjective)
of or relating to Mexico or its inhabitants