The Brownie camera, also known as the Box Brownie, gets its name from its very first 1900 model, which was cased in simple brown leatherette-covered cardboard. Some sources say that the name was also a nod to a popular series of films from the time, Palmer Cox's "Brownies."
The original model, designed to be affordable above all else, did not even feature a viewfinder, so "box" was a very apt description. To further emphasise the box-like nature of the original 1900 model, a push on box lid was used at the back of the camera. This was later replaced by a hinged back after the first type proved unreliable. The camera used a simple lens to focus light onto.
The Brownie is credited with popularising photography because of its simplicity and affordability. Although the camera offered nothing in the way of frills, this made it extremely easy to pick up and use, and its price was very competitive. The fact that it was made of the cheapest possible materials meant that it could be mass-produced easily, and this meant that many homes could afford both the camera and the necessary film.
Later Brownie models retained the name to play on the popularity of the original, but the color range was greatly expanded, with some models coming in two-tone blue, two-tone green, and two-tone rose. Most models, however, stuck with basic black.