Ah, Charlee, you're too young to have had to wear flour sack dresses. During WWII, uniforms took up so much production, fabric always wasn't available. Grandma was able to get good material for my dance costumes, but many of my everyday dresses were flour sacks. Pretty, usually, but not soft and smooth like the percale and silky material for my 'fancy' dresses. Did you catch the switch in terminology? Grandma never called it fabric - either yard goods or material.
A fun find!