registered nurse vs wet nurse

registered nurse

noun
  • A professional nurse who is a licensed graduate of a university or college of nursing who has successfully passed an examination such as NCLEX-RN. 

wet nurse

noun
  • Someone who treats someone else with excessive care. 

  • A woman hired to suckle another woman's child. 

verb
  • To act as a wet nurse (in either sense). 

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