doughboy

dough +‎ boy; its use to refer to an infantryman is unknown, but dates from 1847, during the Mexican-American War.[1]

doughboy (plural doughboys)

1. (US) An American infantryman, especially one from World War I.
   • 1901 July 19, “Horses in time of War”, in The Agricultural Journal and Mining Record‎, volume 4, number 10, page 296:

     The "dough boys" were loaded into army wagons drawn by mules, and with the cavalry at the flanks the relief column started.

   • 1969, Robert L. Vann, The Competitor, volumes 2-3, page 135:

     The miser, a-seeking lost gelt, / The doughboy, awaiting the battle, / May possibly know how I felt / While the long years dragged by as the dealer / As slow as the slowest of dubs, / Stuck out the last helping of tickets / 'Till I lifted—the Bullet of Clubs!

2. A kind of flour dumpling.
3. Frybread.