fucklet vs side piece

fucklet

noun
  • A woman with whom one shares, or hopes to share, a sexual encounter. 

  • A child, regarded as the result of the process of breeding. 

  • A stupid or annoying person. 

  • A sexual encounter of short duration; a quickie. 

side piece

noun
  • A mistress; a woman with whom a man carries on a physical affair (not emotional affair) without having the intention of forming a serious relationship. 

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