You likely have eaten sourdough made with Spelt, one of the Ancient Grains, which is sometimes known as Dinkel Wheat or Hulled wheat. After its use dying out in the middle of last century here in America (It was brought hear from Europe in the late 1800s) the grain has regained popularity with folks looking for more flavorful, healthy and noteworthy flours.
Humans have been cultivating the grain, since about 5000 BC and it was an important staple in Europe through the Middle Ages. It is closely related to regular Hard Red Winter Wheat and has high enough gluten content that bread with a reasonably open crumb can be made from it.
As befits a food that is a staple and has been eaten for 1000s of years, Spelt appears in literature: It is mentioned in the Divine Comedy which likens the transformation of the soul of a suicide victim to the germination of a grain of Spelt and Pushkin references eating Spelt porridge. Greek mythology has Demeter giving Greeks a gift of Spelt.
The Spelt flour you might buy at a natural foods store will more often than not be whole Spelt (equivalent to whole wheat flour). “Whole” is a misnomer – whole wheat or whole Spelt do not include all the products of the berry (kernel) of grain that is milled; rather, the miller has added some of the bran (the exterior coating of the berry) which is stripped off during milling, back into the flour. This is a little like the brown sugar available at supermarkets, which is white sugar that has been refined from sugar cane, with some molasses, extracted during the refining process, added back in for color and flavor.
More accurately, a whole grain flour is one in which the entire wheat berry (endosperm, bran and germ) have been milled together. I have a small mill in which I sometimes mill flour to add to a recipe: this has to be done fresh and the oils in the germ can become rancid unless refrigerated.
White Spelt, like white flour contains the milled portion of the Endosperm only – the outer bran and oily wheat germ have been removed during the milling process. I like using White Spelt in a sourdough loaf as it tweaks the loaf’s flavor and texture: while proofing and shaping the dough has a subtle and inexplicably smooth texture.