He talked to his grandchildren a lot about the “old Texians”.
Out of two of them at least: Wayne (and Richard Boone, I think) used it in The Alamo and later on in True Grit, Wayne addressing Glen Campbell's character. Unless it was an ad-lib by Wayne, the term will have been used in the original novel, too. I'm sure it was heard from time to time in the 19th century.
There was a movie called The Texican in 1966 (Audie Murphy, Broderick Crawford).
Urban Dictionary:
A Texican is person of european decent in Texas. [Originally, an English-speaking colonist, = "Texian".] A Tejano is a person of hispanic decent in Texas.
But modern Tejanos also use the word "Texican" about themselves as well. So you can call them "Mexicans", "chicanos", "Texicans", and "Tejanos".
What I want to know is what all these true-blue Texafarians are going to do about those New Mexico fellers, Raul Grijalva and them no doubt, sending over Zozobra to burn up Big Tex?