the.com/windbag

means A person who talks a lot, usually with great confidence, while saying very little of substance.

from Literally a bag of wind — the word first described an actual bladder or sack full of air (like a bagpipe) before it curdled into an insult for someone whose speech is all puffed-up volume and no real content. The bagpipe connection isn't incidental: early uses leaned on the image of air being forced out noisily and at length. By the 1800s 'windbag' was firmly settled as a label for pompous, long-winded talkers — all bellows, no breath of sense.