adopt vs co-opt

adopt

verb
  • To select and take or approve. 

  • To take voluntarily (a child of other parents) to be in the place of, or as, one's own child. 

  • To take or receive as one's own what is not so naturally. 

  • To obtain (a pet) from a shelter or the wild. 

  • To take by choice into the scope of one's responsibility. 

  • To beat an opponent ten times in a row. 

co-opt

verb
  • To commandeer, appropriate or take over. 

  • To absorb or assimilate into an established group. 

  • To elect as a fellow member of a group, such as a committee. 

How often have the words adopt and co-opt occurred in a corpus of books? (source: Google Ngram Viewer )