The mystique of James Bond is partly personal, from the suave charm and physical daring of the character, and partly technological, from the (very often fanciful) tools of his trade. The formula for most Bond films, along with the gun barrel introduction, the pre-title action sequence, the elaborate schemes of an evil villain, and, at least until recently, sexist and misogynist depictions of women, includes the presentation of esoteric and complicated tools and weapons to be used on his mission.
The first gadget issued to Bond is a very sensible attaché case containing spare bullets and gold coins to help get a stranded agent home from a mission. It also contained a device that released tear gas, something used later in the film to save Bond from a seemingly impossible situation. As the films placed the character in increasingly impossible situations, he was issued with increasingly improbable gadgets, from small underwater breathing devices, ultramagnetic watches, exploding pens, and jetpacks, to cars with the firepower of an army tank that can eject passengers or function underwater like a submarine.
The word gadget is relatively new to English, first attested in the late 1800s. Its precise origin—perhaps appropriate for the name of a spy’s tool—is unknown. The Oxford English Dictionary posits that a possible connection can be made with the French term gâchette, meaning part of a locking mechanism or the trigger mechanism of a gun, but for now there is no convincing proof of this etymology. (No smoking gun, as it were.)
With the more grounded and gritty take on the character as played by Daniel Craig in recent years, the equipment has been more plausible and minimal, to the point where the filmmakers gently mock the excesses of the earlier Bond gadgets.