Cullen is, to be certain, a "good Texas name". Like, say, Grady.
But, as you may recall, the most famous single "Cullen" in Texas history is doubtless Cullen Davis. That would be of the Foat Wuth Davises, y'know.
And just what is Cullen Davis famous for?, non-Texans might ask. Why it was one of the most famous Texas murder cases of all times.
Sometime in the seventies, Cullen Davis allegedly attempted to waste his floozy wife, Priscilla, when she arrived at their mansion, home from a date (Cullen and Priscilla were separated at the time, with Priscilla awarded the family home). In the confusion, Priscilla's daughter ends up getting killed instead (she was double-dating with mom...whole 'nuther story). Priscilla and her boyfriend were only injured in the shootout.
The police came for Cullen, who was, by most all accounts, the guilty party. Enter even more famous Texas criminal attorney, Earl "Racehorse" Haynes. The trial was moved from Foat Wuth to Amarillo on a change of venue, whereupon weeks of jury selection (manipulation) occurred.
Eventually, in a major upset, Cullen Davis was acquitted. But not until Racehorse had separated him from the bulk of the family fortune (which was more than a little substantial).
"Cullen" is, indeed, a real Texas name. And it has a real Texas story behind it...