The word "shack" may derive from the Nahuatl (Aztec) word xahcalli [ʃaʔ'kalːi] or "adobe house" by way of Mexican Spanish xacal/jacal, which has the same meaning as "shack". It was a common usage among people of Mexican ancestry throughout the U.S. southwest and was picked up by speakers of American English.
Oops! I didn't see the slash in between the two spellings of the Nahuatl word. I thought it was just one word.
Should have been just "Radio Shackal" or "Radio Shahckalli".
Other English words from Nahuatl - avocado, chicle, chili, chocolate, copal, coyote, mesquite, ocelot, tomato... and many other names of foods and plants.