cowlet vs heifer

cowlet

noun
  • A young or little cow; a female calf. 

heifer

noun
  • A young female cow, (particularly) one over one year old but which has not calved. 

  • A cow: a large, unattractive, unpleasant woman. 

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