grep /grep/ vi. [from the qed/ed editor idiom g/re/p, where re stands
   for a regular expression, to Globally search for the Regular Expression
   and Print the lines containing matches to it, via {{Unix}} `grep(1)'] To
   rapidly scan a file or set of files looking for a particular string or
   pattern (when browsing through a large set of files, one may speak of
   `grepping around'). By extension, to look for something by pattern.
   "Grep the bulletin board for the system backup schedule, would you?" See
   also {vgrep}.

   [It has been alleged that the source is from the title of a paper "A
   General Regular Expression Parser", but dmr confirms the g/re/p
   etymology -ESR]


Source: The Jargon File

GREP
     Global Regular Expression Print (Unix)
     
     
Source: Virtual Entity of Relevant Acronyms