The Collaborative International Dictionary of English v.0.48:

Denarius \De*na"ri*us\, n.; pl. Denarii. [L. See 2d Denier.]
   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.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

DENARII. An ancient general term for any sort of pecunia numerata, or ready
money. The French use the word denier in the same sense: payer de ses
propres deniers.