If you go back to the roots of this term, you find that there is no racism, nor anything else pejorative in “Mexican Carry.” The lore of the gun tells us that back in the 19th Century, the Mexican vaquero, much like the American cowboy, was an independent and self-reliant sort who often made it a point to carry a handgun. Alas, the history of 19th century Mexico was entailed one despot rising after another. The day came when the average citizen was stripped of his former right to go armed when he wished.
This did not sit well with the fiercely freedom-loving caballeros. They grudgingly took off their gun belts and holsters, because possession of those accoutrements would be seen as evidence that they had violated the draconian new laws that disarmed them. However, they defiantly kept their handguns, simply stuffing them into the waistband behind their ordinary belt. If the Federales hove into view, the citizen would simply slip his revolver into some discreet place where he could retrieve it later.