Source : Free On-Line Dictionary of Computing

hash character
     
         "#", {ASCII} character 35.
     
        Common names: number sign; pound; pound sign; hash; sharp;
        {crunch}; hex; {INTERCAL}: mesh.  Rare: grid; crosshatch;
        octothorpe; flash; {ITU-T}: square, pig-pen; tictactoe;
        scratchmark; thud; thump; {splat}.
     
        The pronunciation of "#" as "pound" is common in the US but a
        bad idea; {Commonwealth Hackish} has its own, rather more
        apposite use of "pound sign" (confusingly, on British
        keyboards the pound graphic happens to replace "#"; thus
        Britishers sometimes call "#" on a US-ASCII keyboard "pound",
        compounding the American error).  The US usage derives from an
        old-fashioned commercial practice of using a "#" suffix to tag
        pound weights on bills of lading.  The character is usually
        pronounced "hash" outside the US.
     
        The name "octothorpe" was made up by a {Bell Labs} supervisor,
        Don Macpherson.
     
        {Octothorpe story
        (http://www.sigtel.com/tel_tech_octothorpe.html)}.
     
        (2003-07-05)