backslash vs expunge

backslash

verb
  • To escape (a metacharacter) by prepending a backslash that serves as an escape character, thereby forming an escape sequence. 

noun
  • The punctuation mark \. 

  • Used erroneously in reference to, or in reading out, the ordinary slash, that is, the punctuation mark /. 

  • |passage= […] I was trying to find a web-site for which I had been given the following address: http://www.isop.ucla.edu/pacrim/pubs/korjournal.htm. […] I began to work backwards, removing first the last part of the address following the last backslash (/korjournal.htm).}} 

expunge

verb
  • To erase or strike out. 

  • To eliminate completely; to annihilate. 

  • To delete permanently (e-mail etc.) that was previously marked for deletion but still stored. 

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