"abacus late 14c., "sand table for drawing, calculating, etc.," from L. abacus, from Gk. abax (gen. abakos) "counting table," from Heb. abaq "dust," from root a-b-q "to fly off." Originally a drawing board covered with dust or sand that could be written on to do mathematical equations. Specific reference to a counting frame is 17c. or later."