The gandō was the Edo flashlight, evolved prematurely under extreme pressure from the highly urbanized population, who loved shadow puppets as fiercely as they hated burglars.

The general principle of the gandō is the same as the modern flashlight: a tube open at only one end and preferably reflective inside, emitting a directed beam of light. However, Edo engineers had no light bulbs, and were obliged to use candles instead. Too prevent the candles falling out and setting fire to the entire city -- again -- they used a simple but ingenious nested-ring design which ensured that the weighted candle-base could always swing around to the bottom, leaving the flame pointing straight up.

To fit the roughly spherical candle-righting mechanism -- which was used in many other types of lantern as well -- the gandō clearly had to be at least as wide as the candle inside it was tall. This made it more like a bucket than a tube, difficult or impossible for anyone sub-Shaq to hold like a modern flashlight, so a large handle would be attached to the rear instead.

All design problems now solved, form obedient to function, the gandō was finally ready to be taken outside and used to illuminate voguing, sunburnt miscreants.

Some gandō were even made of wood, which strikes me as a terrible idea, but I suppose the handle would allow a brief grace period after the barrel caught fire in which to throw it at the intruder.

Language notes: The word gandō is written 強盗, and is short for 強盗提灯, which means "burglar lantern". "Burglar" here is used the same way it is in "alarm": the device is anti-burglar rather than pro-. (The spelling 龕灯 is sometimes used, but this originally referred to a homophonous but different kind of lamp, and the etymology of our gandō is apparently quite clear.)

In modern Japanese, 強盗 in the sense of "burglar" ("robber", really) is pronounced gōtō. This is thanks to the same process that produced the city name Kōbe and the verb ending -ō: /Can/ → /Cau/ → /Co:/. Gandō (chōchin), though, stayed the way it was. The semantic distinction may have been the key, since gandō zukin (強盗頭巾, "burglar hood" -- the kind that hides everything but the eyes) also escaped the sound change.