lambkin vs lovebug

lambkin

noun
  • A term of endearment. 

  • A young lamb, a very young sheep. 

lovebug

noun
  • A person who is in love; a sweetheart. 

  • An insect, the honeymoon fly (Plecia nearctica, family Biblionidae). 

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