abaciscus

The story

1. Ancient Greek · derived fromἀβακίσκος“a coloured stone for laying mosaic”
2. English todayabaciscus

From New Latin, from Ancient Greek ἀβακίσκος (abakískos, “a coloured stone for laying mosaic”), diminutive of ἄβαξ (ábax, “board”). See abacus.

First known use, by meaning

• First attested in the mid 18ᵗʰ century. One of the tiles or squares of a tessellated pavement; an abaculus.