Informal.an American infantryman, especially in World War I.
a rounded mass of dough, boiled or steamed as a dumpling or deep-fried and served as a hot bread.
Origin: 1675–85;dough + boy; sense “infantryman,” from mid-1860s, is obscurely derived; two plausible, but unsubstantiated claims: doughboy orig. referred to the globular brass buttons on infantry uniforms, likened to the pastry; dough referred to a clay used to clean the white uniform belts
"U.S. soldier," 1865, said to have been in oral use from 1854, or from the Mexican-American War (1847), it is perhaps from resemblance of big buttons on old uniforms to biscuits of that name, but there are various other conjectures.