It’s unknown exactly how U.S. service members in World War I (1914-18) came to be dubbed doughboys—the term most typically was used to refer to troops deployed to Europe as part of the American Expeditionary Forces—but there are a variety of theories about the origins of the nickname.
According to one explanation, the term dates back to the Mexican War of 1846-48, when American infantrymen made long treks over dusty terrain, giving them the appearance of being covered in flour, or dough. As a variation of this account goes, the men were coated in the dust of adobe soil and as a result were called “adobes,” which morphed into “dobies” and, eventually, “doughboys.”