Meaning and name origin
Caio \caio\ as a boy's name is of Welsh and Latin origin, and the meaning of Caio is "happy". Caio is a variant of Caeo (Welsh): name of a village and parish in Carmarthenshire (known as the "Garden of Wales") used as a first name in Wales. Also a variant of Cai (Welsh): used as a respelling of Kai in Wales. Caio is also used as a variant of Caius (Latin), Gaius (Latin).
Caio is not a popular first name for males and an equally uncommon surname or last name for all people (2000 U.S. Census).