Updated June 9, 2019 Share: Boy name origins & meanings Latin : Rejoice; variation of GaiusWelsh, German : Rejoicer; fort; joyful Boy name variations Caius Caius + 9% this year Masculine Rare Find out more Cai Cai + 18% this year Masculine Rare Find out more Caio Caio - 6% this year Masculine Rare Find out more Kay Kay + 10% this year Neutral Rare Find out more Keye Keye 0 % this year Masculine Rare Find out more Keyes Keyes 0 % this year Masculine Rare Find out more Keys Keys 0 % this year Masculine Rare Find out more Cais Cais 0 % this year Masculine Rare Find out more Kai Kai + 14% this year Neutral Common Find out more Kaysie Kaysie - 13% this year Neutral Rare Find out more Keh Keh 0 % this year Masculine Rare Find out more MacKay MacKay 0 % this year Masculine Rare Find out more Family name origins & meanings English : variant spelling of Kay 4 and 5.