காசு

Kāsu in Tamil means "coin" or "money." The word is ancient, appearing in Tamil inscriptions from the early centuries CE.

Tamil traders spread the word across the Indian Ocean. In Malayalam it became kāś, in Kannada kāsu, in Telugu kāsu.

Portuguese traders in South India heard "kāsu" and adopted it as "caixa" (money box). Dutch made it "kass," French "caisse," and English "cash."

The Tamil word for coin became the universal word for ready money—cash.