abacus (n.)

late 14c., "sand table for drawing, calculating, etc.," also "art of calculating with an abacus," from Latin abacus, from Greek abax (genitive abakos) "counting table, board for drawing," a word of uncertain etymology. It is said to be from a Semitic source, such as Phoenician or Hebrew abaq "sand strewn on a surface for writing," literally "dust," from the Semitic root a-b-q "to fly off," but Beekes and others find this "semantically weak."

Originally a drawing board covered with dust or sand on which mathematical equations or calculations could be traced and erased. In reference to the other type of abacus, a counting frame with beads or balls strung on wires or rods, it is attested from 17c. or later in English. Both types were known in antiquity across Eurasia. Related: Abacist (late 14c.)