Other forms: fatigues
Fatigue is weakness in metal caused by being flexed too often. Metal fatigue, fatigue cracks, fail from fatigue.
It is why aircraft have a fixed number of flights rather than years of life: a part can be far below its breaking strength and still crack after enough cycles, and the Comet crashes of the 1950s taught the world that lesson. It also means deep tiredness.
French fatigue comes from fatiguer, from Latin fatigare, to weary or harass. The engineering sense borrows the image of a material growing tired.
French
fatigue
English, today
fatigue
Borrowed from French fatigue. From French fatigue, from fatiguer, from Latin fatīgō (“to weary, tire, vex, harass”).
Etymology from Wiktionary, CC BY-SA