In the Edo Period, when the world revolved around samurai takuan was an essential old standby side dish but it was a taboo to serve samurai either one piece or three pieces of takuan in those days.
侍が世の中の中心だった江戸時代、沢庵はおかずに欠かせない定番で、当時、侍に沢庵を一切れ、もしくは三切れだけ出すのはタブーだった。