eardrum vs timpanum

eardrum

noun
  • A thin membrane that separates the outer ear from the middle ear and transmits sound from the air to the malleus. 

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 eardrum and timpanum occurred in a corpus of books? (source: Google Ngram Viewer )