decouple vs sever

decouple

verb
  • To unlink; to take or come apart. 

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

sever

verb
  • To disconnect; to disunite; to terminate. 

  • To make a separation or distinction; to distinguish. 

  • To cut free. 

  • To suffer disjunction; to be parted or separated. 

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