It's from the Latin for "hemp" because it was often made of hemp; add a letter & it means to take a survey
... (Nautical Terms) nautical any cloth of which 
sails are made .... sailing ship, sailing vessel - a vessel that is powered by the 
wind; often... [DOC] [TLE] Spliffs and butts | The Economist [PAR] Sep 21, 2013 ...