archenteron vs cyst

archenteron

noun
  • A primitive alimentary cavity 

cyst

noun
  • A pouch or sac without opening, usually membranous and containing morbid matter, which develops in one of the natural cavities or in the substance of an organ. 

  • Of or pertaining to the urinary bladder or gall bladder (in compounds). 

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