(Hebrew > Greek > Latin > Middle English: dust)

abacist (s) (noun), abacists (pl)
A person who is skilled in using an ancient form of a calculator consisting of counters that are moved in a groove or on a wire to represent a variety of numbers: In school during her math lesson Susan learned that math was often done in earlier times on an abacus by abacists who often used them at the market for calculating the costs of their wares.
abacus (s) (noun), abaci (pl)
1. A manual computing device consisting of a frame holding parallel rods strung with movable counters: Before numbers were even developed as such, counting devices were used to perform everyday calculations; one of these devices was the abacus, which provided merchants accurate data when buying or selling products.
2. A calculator that performs arithmetic functions by manually sliding counters on rods or in grooves: A more recent form of the abacus consists of a frame often made of wood which firmly holds a set of rods or wires with freely sliding beads mounted on them.

The abacus as we know it today doesn't appear as it did when it was originally invented. In ancient times, the abacus was a simple device that was used to count numbers; this only included addition and subtraction.

The newer abaci contain four decks, in which more complex operations can be made; including multiplication and division and they include instructions for determining square roots and cubic roots of numbers.

3. In architecture, a slab or tablet placed horizontally on the top and that filled the space between the columns as an aid in supporting the architrave, the lowest flat stones of structural elements that were on the top of columns: In classical architecture, the shape of the abaci and their edge profiles varied in the different Greek and Roman classical orders.

4. Etymology: a Latin word from the Greek word abax, "counting table". The original abaci were created in sand.

The Abacus, a History

The source of our word abacus, the Greek word abax, is thought to come from Hebrew 'abaq, "dust", although the details of such a transmission are obscure. In postbiblical usage 'abaq meant "sand used as a writing surface".

The Greek word abax has as one of its senses "a board sprinkled with sand or dust for drawing geometric diagrams."

The difference in form between the Middle English word abacus and its Greek source abax is explained by the fact that Middle English actually borrowed Latin abacus, which came from the Greek genitive form (abakos) of abax.

The abacus is the ancestor of the modern calculating machine and computer

The earliest abacus probably was a board or slab on which a Babylonian spread sand so he could trace letters for general writing purposes.

As the abacus came to be used solely for counting and computing, its form was changed and improved.

The sand or "dust" surface is thought to have evolved into the board marked with lines and equipped with counters whose positions indicated numerical values; such as, ones, tens, hundreds, and so on.

In the Roman abacus the board was given grooves to facilitate moving the counters in the proper files while another form, common today, has the counters strung on wires.

The abacus, generally in the form of a large calculating board, was in universal use in Europe in the Middle Ages, as well as in the Arab world and in Asia.

It reached Japan in the 16th century. The introduction of the Hindu-Arabic notation, with its place value and zero, gradually replaced the abacus, although it was still widely used in Europe as late as the 17th century and survives today in the Middle East, China, and Japan.

An expert abacus practitioner can often successfully compete against many modern mechanical calculating machines.

A skilled abacus user, or soroban as it is called in Japan, can perform in a fraction of time, a difficult arithmetic calculation that others could do laboriously only by means of pencil and paper. The Japanese tradesman with his soroban can even outstrip a rapid and accurate Western accountant with his or her electronic adding machine.

—This last section was compiled from information located in
"abacus", Encyclopaedia Britannica Online.