envelope vs weather balloon

envelope

noun
  • A bag containing the lifting gas of a balloon or airship; fabric that encloses the gas-bags of an airship. 

  • Something that envelops; a wrapping. 

  • An enclosing structure or cover, such as a membrane; a space between two membranes 

  • A curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics. 

  • A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects. 

  • A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing. 

  • The nebulous covering of the head or nucleus of a comet; a coma. 

  • The set of limitations within which a technological system can perform safely and effectively. 

  • The shape of a sound, which may be controlled by a synthesizer or sampler. 

  • The information used for routing a message that is transmitted with the message but not part of its contents. 

  • An earthwork in the form of a single parapet or a small rampart, sometimes raised in the ditch and sometimes beyond it. 

weather balloon

noun
  • a balloon that carries meteorological instruments aloft in order to measure, record and return data concerning atmospheric pressure, temperature and humidity 

How often have the words envelope and weather balloon occurred in a corpus of books? (source: Google Ngram Viewer )