means An enclosed chamber that cooks, bakes, or heats food (or anything else) by surrounding it with sustained dry heat.

from From Old English 'ofen,' a baking chamber, going back to a Proto-Germanic root (compare German 'Ofen,' a stove or furnace) and ultimately a Proto-Indo-European word for a cooking pot or vessel. So long before it was a steel box with dials, it was simply the thing you put on the fire to bake — a name almost as old as bread itself.