cling to vs foster

cling to

verb
  • To have an intense emotional dependency on (someone). 

  • To remain by (someone's) side; to refuse to leave the company of. 

  • Used other than figuratively or idiomatically: see cling, to. 

foster

verb
  • To nurse or cherish something. 

  • To cultivate and grow something. 

  • To nurture or bring up offspring, or to provide similar parental care to an unrelated child. 

adj
  • Related by such care. 

  • Receiving such care. 

  • Providing parental care to children not related to oneself. 

noun
  • A foster parent. 

  • The care given to another; guardianship. 

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