pistol (n.)

"small firearm with a curved handle, intended to be held in one hand when aimed and fired," 1570s, from Middle French pistole "short firearm" (1566), a word of uncertain origin, sometimes said to be from German Pistole, from Czech pis'tala "firearm," literally "tube, pipe," from pisteti "to whistle," a word of imitative origin, related to Russian pischal "shepherd's pipe."

But the earlier English form pistolet (1550) is said to be from Middle French pistolet "a small firearm," also "a small dagger," which is said to be connected with Italian pistolese, in reference to Pistoia, the town in Tuscany noted for gunsmithing.

Pistol-whip (v.) "strike (someone) with the butt of a pistol is recorded by 1942. Pistol-grip "handle shaped like the butt of a pistol" is by 1874.