The Abacus, a History
abacus (Hebrew > Greek > Latin > Middle English: dust).
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.
abacus, singular; abaci, plural:
1. A manual computing device consisting of a frame holding parallel rods strung with movable counters.
2. In architecture, a slab on the top of the capital of a column.