from The Century Dictionary.
- noun A cap of iron, fitted to the top of a pipe, as in an oil-well, to receive the blow when driven and thus to protect the pipe.
Sorry, no etymologies found.
Marengo surveyed them gloomily from under a driving-cap visor huge as a sugar-scoop.
Blount pushed his driving-cap back, mopped his face, and came around to dive once more into the wiring in the battery box.