Why is the loose-fitting clothing worn by soldiers called army fatigues?
Army fatigues (such as those worn in the picture below) are donned by soldiers when performing menial, nonmilitary tasks. These tasks themselves were once referred to as fatigues, which is where the G.I. garb got its name (originally: fatigue dress, "outfit worn when performing fatigues").
The chores (and thus the clothing) were so-called for being tiresome and laborious.
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