Hyotan or hisago (gourds), sometimes known as bottle gourds, are a popular motif in Japan.
In Symbols of Japan: Thematic Motifs in Art and Design Merrily Baird writes that the Chinese believed that the double shape of a gourd symbolized heaven and earth, and that the hyotan’s numerous seeds suggested a connection with rebirth and immortality. Those beliefs were undoubtedly exported to Japan. A famous Japanese proverb — hyotan de namazu o osaeru — also compares a difficult task to be like “trying to catch a catfish with a gourd.”
in the pre-modern period Japanese men often carried a small gourd on a toggles at their waist, while during the same period women had them engraved on their footwear as a talisman to prevent tripping.
Hollow hyotan are sometimes used as canteens or flower holders, and historically were used to serve sake. I have a hyotan that I bought in Indiana that was made into a small bird house. I think they’re the perfect shape for hashioki because the area between the two bulges is just right for the tips of two chopsticks.
Hyotan have a military connection, too, through Shogun Totomi Hideyoshi (1536-1598). Some stories say that Hideyoshi adopted the hyotan as his battle emblem as a nod to his peasant origins, while others claim that he won a significant military victory when a gold hyotan was hoisted on top of a pole as his ensign. Both stories, of course, may be true.