gasbag vs hot-air balloon

gasbag

noun
  • A lighter-than-air aircraft; a balloon or dirigible. 

  • A bag or bladder to hold a reservoir of gas, as in a hot-air balloon. 

  • A person who is overly garrulous or prone to making empty, unsupportable statements; a windbag. 

verb
  • To speak foolishly, pompously, or at length; to blather. 

hot-air balloon

noun
  • A balloon-shaped aircraft whose bag is inflated with hot air; it carries passengers and crew in a gondola slung underneath. 

How often have the words gasbag and hot-air balloon occurred in a corpus of books? (source: Google Ngram Viewer )