amnion vs caul

amnion

noun
  • The innermost membrane of the fetal membranes of reptiles, birds, and mammals; the sac in which the embryo is suspended. 

caul

noun
  • A membrane. 

  • The amnion which encloses the foetus before birth, especially that part of it which sometimes shrouds a baby’s head at birth (traditionally considered to be good luck). 

  • The surface of a press that makes contact with panel product, especially a removable plate or sheet. 

  • An entry to a mill lead taken from a burn or stream (a mill lead (or mill waterway) is generally smaller than a canal but moves a large volume of water). 

  • Caul fat. 

  • A strip or block of wood used to distribute or direct clamping force. 

  • A style of close-fitting circular cap worn by women in the sixteenth century and later, often made of linen. 

  • The thin membrane which covers the lower intestines; the omentum. 

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