Young H. Rhie sent me a little gem about the origin of the term Ko, and here's my version of it:
"Originally, Ko is a Buddhist term, the original term is Kalpa. Kalpa describes a long timespan - from the beginning of the cosmos till its destruction.
Another description of Kalpa:
There is a stone measuring 10 x 10 x 10 km. Every 100 years, a fairy's dress gently brushes it. It will take "Kalpa" for the stone to be eroded fully away by her soft garment.
If there would not be a Ko rule in Go, it could take Kalpa before the game finishes.
The Korean term for Ko is Pae. Pae means "Struggle to win". The Korean term is more descriptive than the Japanese and Chinese terms, but the Japanese and Chinese terms for Ko are more philosophical."