currency

Currency traces back to the Latin verb currō, "I run," whose present participle currēns meant "running." Medieval Latin turned this into the noun currentia, which English borrowed as currency — literally the state of being current, or in circulation.

The word's core sense stayed close to motion: something flowing or running along. From that idea of continuous flow, English speakers applied it to money that circulates, and by extension to whatever is widely accepted or in common use.

Currency shares its root with current, since English currency is essentially current plus the ending -cy — the state or quality of being current.