Kaius is a modern spelling of Caius, a form of the Roman first name Gaius, whose meaning is uncertain and traditionally linked to the Latin gaudere, "to rejoice". The K spelling ties it to the popular Kai while keeping the classical ending of Titus and Cyrus. In the United States Kaius has sat between number 1000 and 1700 for a decade, came closest to the top 1000 at number 1023 in 2020 and ranks number 1029 in 2025.