The history of ponzu is very interesting. Although it is a condiment unique to Japan, the origin of the word is not Japanese. The name "ponzu" was originally derived from the Dutch word "pons," which refers to certain alcohol and citrus fruits, and was adopted into the Japanese language. The Netherlands was the only Western country that traded with Japan during a certain time of the Edo period (1603-1868), when the country was closed to the the rest of the outside world (precisely 1641-1853). At that time, pons were introduced to Japan from the Netherlands as an aperitif, but it eventually became a word for the citrus juice used in pons, and the word became Japanese. It is said that pons were often drunk by Dutch sailors on Dejima Island in Nagasaki. Incidentally, the kanji for "zu" (酢) in ponzu means "vinegar," said to be because it had a sour taste like vinegar. Originally, ponzu did not contain vinegar, but the kanji character for "vinegar" was applied to it to mean something sour.