A shack is a type of small house that is in disrepair. The word may derive from the Nahuatl (Aztec) word xacalli or "adobe house" by way of Mexican Spanish xacal/jacal, which has the same meaning as "shack"http://www.bartleby.com/61/75/S0307500.html. It was a common usage among people of Mexican ancestry throughout the U.S. southwest from the 19th century if not earlier.