Kasai is a modern American choice with no single established meaning: it is best known as the name of the "Kasai River", one of the great tributaries of the Congo in Central Africa, and it also occurs as a Japanese surname. For American parents it fits the sound of Kai, Kasen and Kairo. The name is one of the fastest risers of 2025: it was number 1747 in 2024 and jumped into the top 1000 for the first time at 639.