abacus — ONAD

abacus /ˈabəkəs, ˈæbəkəs

▸ noun

(plural abacuses)

1 an oblong frame with rows of wires or grooves along which beads are slid, used for calculating.

2 Architecture the flat slab on top of a capital, supporting the architrave.

– ORIGIN late Middle English (denoting a board strewn with sand on which to draw figures): from Latin, from Greek abax, abak- ‘slab, drawing board’, of Semitic origin; probably related to Hebrew 'āḇāq ‘dust’.