nundine

Meanings

1. A market or fair held every eight days, particularly (historical) in Roman contexts.
2. Any recurring eight-day period; an eight-day 'week'.

Etymology

From Latin nundinae (“ninth-days”), a clipped form of nundinae feriae (“ninth-day festivals”), from its observance every eighth day (9 counting inclusively) and from the Latin practice of treating most recurring calendrical days as plurals.