Kain is a spelling variant of Cain, the Hebrew name of Adam's first son, usually explained as "acquired" or "spear"; it also doubles as a short form of the Irish surname Kane, "warrior". The K spelling softens the biblical association and gives the name a modern, punchy look. In the United States Kain reached number 1093 in 2016 and ranks number 1738 among boys' names in 2025.