mammal vs pet

mammal

noun
  • An animal of the class Mammalia, characterized by being warm-blooded, having hair and producing milk with which to feed its young. 

  • A vertebrate with three bones in the inner ear and one in the jaw. 

pet

noun
  • An animal kept as a companion. 

  • Something kept as a companion, including inanimate objects. (pet rock, pet plant, etc.) 

  • One who is excessively loyal to a superior and receives preferential treatment. 

  • A fit of petulance, a sulk, arising from the impression that one has been offended or slighted. 

  • Any person or animal especially cherished and indulged; a darling. 

  • A term of endearment usually applied to women and children. 

adj
  • Favourite; cherished; the focus of one's (usually positive) attention. 

  • Kept or treated as a pet. 

verb
  • To stroke or fondle (another person) amorously. 

  • To stroke or fondle (an animal). 

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