Trapa natans, commonly known as European water chestnut, water caltrop, or devil pod, is an aquatic annual floating plant in the family Lythraceae. The name derives from Latin trapa, meaning “thistle,” referencing its barbed fruit, which resembles a horned nut. Native to Eurasia and Africa, it has a long history of cultivation in South and East Asia. Archaeological finds show it was consumed in Neolithic Europe, particularly around lake settlements, and it became a staple in ancient China and India, where it was valued both as food and medicine.

The edible part is the starchy seed (nut) enclosed in a hard, horned shell. Traditionally, it was roasted, boiled, or ground into flour for making cakes and porridge. In Chinese cuisine, it is used in desserts, festival foods, and herbal preparations, while in India, the dried flour (singhara flour) is widely used in fasting recipes and sweets. Modern uses extend to snacks, confections, and health foods. Though highly nutritious, containing carbohydrates, protein, and minerals, raw seeds can sometimes harbor toxic secondary metabolites or serve as vectors for parasites if harvested from contaminated waters, making proper cooking essential.