Meaning and Name Origin
Caio \caio\ as a boys' name has the meaning "happy". Caio is a variation of Caeo (Welsh): name of a village and parish in Carmarthenshire. Caio is also a variation of Cai (Welsh): used as a respelling of Kai in Wales. Caio is also used as a derivative of Caius (Latin) and Gaius (Latin).
Caio is an uncommonly occurring first name for men. Caio is an unusual last name too for both adults and children. (2000 U.S. Census)
Below is a graphed comparison of the usage of Caio and associated names. Popular variation forms of Caio (#unlisted) ranked in the Top 1000 are Kai (#177 in 2014) and Kay. These boy names are at the apex of their popularity presently, except for the form Kay which has become less stylish. Kai (#177) is the most contemporarily stylish name for newborns among these. (2014 Birth Statistics)