Zimmer frame vs tramper

Zimmer frame

noun
  • A walking frame. 

tramper

noun
  • A recreational hiker. 

  • A mechanism which pounds material into a more compact form for further processing; found for example in cotton gins and trash processors. 

  • A ship, typically a bulk freighter, which does not travel on a fixed route; compare liner. 

  • One who tramps. 

How often have the words Zimmer frame and tramper occurred in a corpus of books? (source: Google Ngram Viewer )