Lazy attempt at providing some answers at least: https://www.lifewire.com/car-cigarette-lighter-12v-socket-534754 https://www.lifewire.com/car-cigarette-lighter

Lazy attempt at providing some answers at least: https://www.lifewire.com/car-cigarette-lighter-12v-socket-534754 https://www.lifewire.com/car-cigarette-lighter-12v-socket-53.... Excerpt: Although they weren’t originally designed with this purpose in mind, car cigarette lighters provided an opportunity that was simply too good to pass up. Since the actual lighter portion was removable once the coil-and-reel version fell out of use, the receptacle itself provided easy access to power and ground. That allowed for the development of a power plug that could be inserted and removed with no need to permanently wire an accessory into the electrical system of a car. The ANSI/SAE J563 specification was developed to ensure compatibility between cigarette lighter receptacles and 12V power plugs made by different manufacturers.