backslash vs tract

backslash

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).}} 

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

tract

noun
  • A brief treatise or discourse on a subject. 

  • Part of the proper of the liturgical celebration of the Eucharist for many Christian denominations, used instead of the alleluia during Lenten or pre-Lenten seasons, in a Requiem Mass, and on a few other penitential occasions. 

  • A series of connected body organs, such as the digestive tract. 

  • A commentator's view or perspective on a subject. 

  • Continued or protracted duration, length, extent 

  • An area or expanse. 

  • A small booklet such as a pamphlet, often for promotional or informational uses. 

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