The term "windbag" is a vivid compound noun formed from two common Old English and Old Norse roots. Literally, it denotes a bag for holding wind, such as a bellows or bagpipes. By the early 19th century, this concrete image was applied metaphorically to a person, comparing their incessant, inflated, and often meaningless speech to the empty air contained in a bag. The logic is elegantly pejorative: just as a bag of wind is full of nothing substantial, a windbag is viewed as a container for boastful or tedious talk lacking real value.

Structure: wind (air in motion) + bag (flexible container) - wind: From Old English wind, of Germanic origin; related to Dutch wind and German Wind, from an Indo-European root shared by Latin ventus. In this compound, it carries the metaphorical sense of "empty or insubstantial talk." - bag: From Old Norse baggi, of Germanic origin. In this compound, it functions as a container, metaphorically holding the "wind" of words.