To cut a long story (which is worth reading in full) short, his dictionary relates it to the Hebrew word 'Avak' -- dirt. The original abacuses, he says, were basically just boxes of dirt or sand in which geometrical diagrams could be drawn and calculations made -- and then erased.
But why, he asks, should this word come from the Hebrew, and not for example from the Phoenician 'Abak,' meaning sand?
This would seem a more plausible derivation, were it not for a curious and generally misunderstood Hebrew phrase that we find in the Talmud.All very brilliant. But his theory has one weakness: why would a scribe need a box in which he can write, in dust, words and sums that can then be erased? It's hard to imagine.
This phrase is avak sofrim, literally "scribes' dust," and it occurs in a passage in the Mishnaic tractate of the Sabbath. In a discussion of whether or not writing is permissible on the Sabbath, we read:
"Writing with ink, with arsenic, with chalk, with tree gum, with copper sulfate, or with anything that leaves a [permanent] impression is forbidden.... Writing with beverage, with fruit juice, in ordinary dirt [avak drakhim], in scribes' dust [avak sofrim], or in anything impermanent is permitted."
What does "scribes' dust" mean in this passage? If you look up avak sofrim in a Hebrew dictionary, you will read: "A powder scattered by ancient scribes on ink to dry it." In turn, this is based on traditional rabbinic interpretations of the phrase, such as Rashi's comment that it refers to "the powdered dust [afrurit] in a scribe's jar."
However, a moment's reflection should convince one that this is illogical. If writing in ink is forbidden on the Sabbath because it is permanent, how could dusting the ink to dry it be permitted? This makes no sense at all.Indeed, here "scribes' dust" can mean only one thing: fine dirt or sand kept by a scribe, not in a jar to powder ink but in a box so that it can be used to write erasable and therefore impermanent words or sums. One can only assume that the 11th-century Rashi made such a mistake because by the time he lived, the rod-and-bead abacus had replaced the obsolete sand abacus.
I do have one suggestion, however, which would really strengthen Philologos's case for a connection between the abacus and "Avak Sofrim." Perhaps, instead of "Avak Sofrim" being translated as "Scribe's Dust," it should really be translated as "Counter's Dust" (as in, 'lisfor,' to count) -- ie., the reference in the Mishnah was to an abacus all along?