Kai has several independent origins: in Hawaiian it means "sea" or "ocean", in Scandinavia and the Netherlands it is a short name of uncertain origin that has been in use since the Middle Ages, and in Japanese and Chinese it can be written with characters meaning "ocean" or "open". That makes it a true global name that works in almost any language. Kai ranked number 403 in 2000, reached the top 100 in 2019, peaked at number 59 in 2022 and sits at number 93 in 2025.