Why are uniforms called fatigues?

Fatigue is a basic part of today’s vocabulary, but, surprisingly, only dates back to the mid-17th century in English. It’s not used even a single time by Shakespeare or in the King James Bible. It came to English from French and ultimately derives from the Latin verb fatigare, meaning “to tire out” or “to exhaust.” An earlier direct borrowing into English from Latin, fatigate, was used in the 1500s before disappearing (it’s now labeled obsolete in our dictionaries). Fatigue entered English first as a noun, then the verb (“the work fatigues me”) and adjective (“a fatigue detail”) came along. The noun was used to mean both “the state of being tired” and “labor,” “effort,” or “trouble”—a sense that seems old-fashioned today. Early uses of fatigue meaning “effort” or “labor” often were in military contexts:

the fatigue of our long march

the fatigues of war

the fatigues of a long journey

they no longer have fatigue without pay

toil and fatigue

These senses led to two military-specific uses of fatigue. First, it came to mean “manual or menial work performed by military personnel,” and then, consequently, “the uniform or work clothing worn on fatigue detail and in the field.” This is how fatigues came to mean “uniform” in the military. When your job seems to be all work and no play, even your clothes are tired.