lovebird vs valentine

lovebird

noun
  • One of the members of an openly affectionate couple. 

  • Any small parrot from one of the nine species within the genus Agapornis. Sometimes they are kept as cage birds and are noted for their affection towards each other. 

verb
  • To express romantic affection openly. 

valentine

noun
  • An expression of affection, especially romantic affection, usually in the form of greeting card, gift, or message given the object of one's affection, especially on February 14th. 

  • A person to whom a valentine is given or from whom it is received, especially on February 14th. 

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