from
The Collaborative International Dictionary of English v.0.48
Nundinal \Nun"di*nal\, Nundinary \Nun"di*na*ry\, a. [L.
nundinalis, nundinarius, fr. nundinae the market day, the
weekly market, prop., the ninth day, fr. nundinus belonging
to nine days; novem nine + dies day: cf. F. nundinal.]
Of or pertaining to a fair, or to a market day.
[1913 Webster]
{Nundinal letter}, among the Romans, one of the first eight
letters of the alphabet, which were repeated successively
from the first to the last day of the year. One of these
always expressed the market day, which returned every nine
days (every eight days by our reckoning).
[1913 Webster]