cart-, carto-

(Greek > Latin: map; card [playing]; a piece of papyrus, paper)

cartridge
1. A cylindrical, now usually a metal casing containing the primer and charge of ammunition for firearms.
2. A casing fitted with a bullet and a similar piece of ammunition: such as, a shotgun shell.
3. A case filled with high explosives, used in blasting
4. A small modular unit designed to be inserted into a larger piece of equipment; such as, an ink cartridge. 5. A removable case containing the stylus and electric conversion circuitry in a phonograph pickup.
6. A case containing magnetic tape in a reel; a cassette; or a case containing a ribbon in a spool, for use in printers and electric typewriters.
7. A lightproof case with photographic film that can be loaded directly into a camera.
8. Etymology: a corruption of French cartouche, "a full charge for a pistol"; from Itatlian cartoccio, "roll of paper"; a form of Middle Latin carta, "paper".

The notion is of a roll of paper containing a charge for a firearm; such as, a pistol or a rifle.