"How did the 32nd Division pick up its original 'Iron Jaw Division' nickname?" was a question asked at the July 18, 2017 #32ndDivisionanniversary event. Well, we didn't know at the time, but now we do!
The name emerged in early October 1917 during the first week Wisconsin and Michigan troops were at Camp MacArthur, Texas. The best we can tell is that the division got its nickname because its Soldiers were "so physically fit and ready for service at any time." The nickname never really took off and only scattered references were found going forward. (OSHKOSH DAILY NORTHWESTERN, Oct. 1, 1917).