suckle vs wet-nurse

suckle

noun
  • An act of suckling 

verb
  • To nurse from (a breast, nursing mother, etc.). 

  • To give suck to; to nurse at the breast, udder, or dugs. 

  • To nurse; to suck milk from a nursing mother. 

wet-nurse

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