madam vs side piece

madam

noun
  • The mistress of a household. 

  • A woman who runs a brothel, particularly one that specializes in finding prostitutes for rich and important clients. 

  • A polite form of address for a woman or lady. 

  • A conceited or quarrelsome girl. 

  • An irritable, conceited, or contemptous woman. (used as a general term of abuse). 

verb
  • To address as "madam". 

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 madam and side piece occurred in a corpus of books? (source: Google Ngram Viewer )