Hi,
It seems that the Tlax in question refers to San Esteban de Nueva Tlaxcala was a Tlaxcalan municipality in what is now the Mexican state of Coahuila.

Research shows that San Esteban was the northernmost of the six Tlaxcalan colonies established in 1591 at the behest of viceroy Luis de Velasco; its founders came from Tizatlan.

In 1827, San Esteban was merged into the city of Saltillo.

Hope this helps!