khoums

Etymology
From.

Noun

 * 1) A subdivision of the Mauritanian ouguiya. 5 khoums equal one ouguiya.

Usage notes
The final /s/ is an integral part of the Arabic root for 'five', so the singular should be khoums. However, the letter has sometimes been mistaken for the English or French plural ending, and a new singular khoum created by back-formation.