A ducat is a gold coin. Ducat sounds like “duckit” and was used as European currency until the early 20th century.
Ducat is an Italian word related to duke. If you recognize this word, you might know it from William Shakespeare’s Hamlet, in which the hero shouts “Dead, for a ducat, dead!” Also, ducat is mentioned so often in The Merchant of Venice that it was slang for “money” or “ticket” for a long time after. But don’t ask for your change in ducats; the cashier probably won’t know what you’re talking about.