middle ear vs timpanum

middle ear

noun
  • The cavity in the temporal bone between the eardrum and the inner ear that contains the ossicles, and which conveys sound to the cochlea. 

timpanum

noun
  • The eardrum. 

  • A kettledrum. 

  • The diaphragm of a telephone. 

  • The middle ear. 

  • An external hearing organ in some insects. 

  • An ornamental panel in any triangular space. 

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