decouple vs unhitch

decouple

verb
  • To unlink; to take or come apart. 

  • To muffle the seismic waves of (a nuclear explosion) by performing it underground. 

unhitch

verb
  • To disconnect; to detach; to undo that which is hitched. 

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