They tell me that "Tako Kabanya" (蛸鞄屋) means "Octopus Bag Shop" in Japanese. That's relevant because "Tako Kabanya" sounds very much like "Taco Cabaña". The fast food chain has Anglicized the spelling and pronounciation to Taco Cabana.
It's still funny when they ask if you want to go in on a dinner order from Octopus Bag Shop.
Edit: ndrtoon posts that the phrase he and his brother came up with was actually "Octopus Bag Store". I'm glad to have a correction from one of the originators.