ancient Roman silver coin, 1570s, from Latin denarius, noun use of adjective meaning "containing ten," and short for denarius nummus "the coin containing ten (aces)," from deni- "by tens," from decem "ten" (from PIE root *dekm- "ten"). In English money reckoning, "a penny," this having been, like the Roman denarius, the largest silver coin (hence d for "pence" in l.s.d.).
