Someone who is pompous and conceited is called
a ‘stuffed shirt’. Their description goes back to American women’s
fashion in the early 1900’s. At that time, women wore ‘shirtwaists’.
These were dresses or blouses tailored like shirts.
As dummies were not yet in existence, stores displayed the garments
in their show windows stuffed with tissue paper. They may have
looked good from afar, but on closer inspection they proved to be
flimsy, without substance.