Kallen is an American variant of Callan and Kellen, surnames of Irish origin usually traced to Ó Cathaláin, from cath, which means "battle". The K spelling matches the style of Kaden and Kolten and keeps the name in step with current sounds. Kallen stood at number 2953 in 2000, peaked at number 1178 in 2014 and ranks number 1302 in 2025.