The Free On-line Dictionary of Computing (30 December 2018):

hash character
octothorpe

    "#", 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://sigtel.com/tel_tech_octothorpe.html).

   (2003-07-05)