As Kaleko says, the
German word is "
Kai". This is from Dutch "kaai", but it is said to go back to a Gaulish word "caio" meaning "enclosure, hedge". Some say, the name
Kai (or
Kay,
Cai, Cei) in the story of
King Arthur may be derived from this word.
KAI has also been explained as a Frisian variant of
KLAUS (Kaei > Klaei > Klais >
Klaes).
Others say, it's a Frisian short form of
Gerhard.
CAIUS seems indeed to be of obscure origin. Some tries:
- "Man from Caieta" (a city now called Gaete, nw of Naples)
- from Greek "gaios" (rural)
- from Greek "gaio" (I am happy)
This is not neccessarily from reliable sources. Obscure indeed.
This leaves
Sky Dumont, the actor. The story has it, that his elder brother misunderstood the name, when his mother returned from hospital with the new born baby.
Sky's name was
Cayetano and his mother said to his brother: "This is Cay." But he heard "This is
Sky."