from The Century Dictionary and Cyclopedia
- n. A small, light cap worn by soldiers when on fatigue-duty.
Sorry, no etymologies found.
He exchanged a cake of chocolate for a fatigue-cap and fell in with them.
Countess was busy somewhere with Buckhurst, who had come with news for her, and the German surgeon's sharp double rap at the door did not bring her, so I called out, "Entrez donc!" and he stalked in, removing his fatigue-cap, which action distinguished him from his brother officers.
He was almost as dark as an Indian, his hair was long enough to reach to his shoulders, and the eyes that looked out from under the peak of his fatigue-cap were as black as midnight and as sharp as those of an eagle.
They had scarcely left the ruins when a fatigue-cap arose from behind a pile of rubbish scarcely a dozen feet from the place where the three conspirators had been sitting, and a pair of eyes looking out from under the peak of that cap watched them as they moved away.
As he placed the jaunty fatigue-cap over his long, curly hair he looked rather complacently at the handsome face and figure that were reflected from the polished surface of the mirror.
-- And lo! suddenly, one autumn morning, into the courtyard of my house dashes a calash drawn by a pair of splendid trotters, with a monstrous coachman on the box; and in the calash, wrapped in a cloak of military cut with a two-arshín  beaver collar, and a fatigue-cap over one ear -- _à la diable m'emporte_ -- sits Mísha!
Philippe kept silence as he looked at the man, whose boots were worn out, his trousers torn in a dozen places, while nothing but a ragged fatigue-cap covered with ice was on his head.