Denarius

·noun A Roman silver coin of the value of about fourteen cents; the "penny" of the New Testament;

— so called from being worth originally ten of the pieces called as.

denarius
dēnārĭus, a, um, adj. [deni], containing ten. I In gen.: numerus digitorum, Vitr. 3, 1: fistula,...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
denarius
dēnārius (genplur. -iūm; rarely -iōrum), adj.deni, containing ten each ; hence, worth ten (asses)...

An Elementary Latin Dictionary
Denarius
(containing ten), Authorized Version "penny," (Matthew 18:28; 20:2,9,13) a Roman silver coin in the ...

William Smith's Bible Dictionary