cable tray vs plumbing

cable tray

noun
  • A rigid structure to support electric cables; a type of raceway, normally having the appearance of a ladder and open at the top to facilitate changes. 

plumbing

noun
  • The pipes, together with the joints, tanks, stopcocks, taps, and other fixtures of a water, gas, or sewage system in a house or other building. 

  • A system of vessels or ducts in the human body, especially the genitourinary system. 

  • The trade or occupation of a plumber. 

  • Practical, concrete work serving to support other work. 

  • A Murasugi sum where each disk summed along has its boundary subdivided into four segments. 

How often have the words cable tray and plumbing occurred in a corpus of books? (source: Google Ngram Viewer )