Gadget

Gadget: An everyday word applied colloquially to any mechanical contrivance or detail, usually small and easily removable. Also, a makeshift, substitute word for anything, when the right word does not readily occur to a speaker. For instance, a man fumbling with the buckle of a strap might say he couldn't get "this gadget to work!"

Originally, a Navy word and then adopted in technical branches of the Army, and in the end becoming used universally. Probably derived from the French word Gâchette.