duct vs inner tube

duct

noun
  • a tube or elongated cavity (such as a xylem vessel) for conveying water, sap, or air 

  • a vessel for conveying lymph or glandular secretions such as tears or bile 

  • a pipe, tube or canal which carries gas or liquid from one place to another 

  • a layer (as in the atmosphere or the ocean) which occurs under usually abnormal conditions and in which radio or sound waves are confined to a restricted path 

  • an enclosure or channel for electrical cable runs, telephone cables, or other conductors 

verb
  • to enclose in a duct 

  • to channel something (such as a gas) or propagate something (such as radio waves) through a duct or series of ducts 

inner tube

noun
  • An inflatable rubber tube inserted into the casing of a pneumatic tyre/tire. 

  • Synonym of swim ring 

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