nipple vs vacuum tube

nipple

noun
  • A short tube threaded at both ends, used as a connector. 

  • The projection of a mammary gland from which, on female mammals, milk is secreted. 

  • A mechanical device through which liquids or gases can be passed in a regulated manner. 

  • Any small physical protrusion, such as the lumps on the F and J keys on computer keyboards. 

  • A perforated segment that fits into part of the breech of a muzzle-loading gun, on which the percussion cap is fixed. 

  • Any small physical protrusion on an automotive, a machine part or any other part that fits into a groove on another part. 

  • An internally threaded piece which holds a bicycle spoke in place on the rim. 

  • An artificial nipple (definition 1) used for bottle-feeding infants. 

  • A pointing stick. 

verb
  • To fit (a baby's bottle, etc.) with a nipple. 

  • To give one's nipple to (a baby) to allow breastfeeding. 

vacuum tube

noun
  • A type of electron tube that controls electron current through vacuum between electrodes within a sealed container, usually of glass or metal and often designed to be easily installed in and removed from the equipment in which it is used. 

How often have the words nipple and vacuum tube occurred in a corpus of books? (source: Google Ngram Viewer )