Ko seemingly is a buddhist term (from sanskrit kalpa) describing "an enormous passage of time, the next thing to eternity." (Source: Kawabata's Master of Go, ISBN 0-679-76106-3, footnote 39)
The original Chinese word ko means to rob. (Source: Go History at yutopian.com)
However, the Japanese term ko literally means "threat" (which means a ko threat would be redundant :) )
What? I thought it meant "eternity", i.e. the same as in the sanskrit and so forth.
exswoo That's the secondary meaning of the same kanji. A ko situation would involve both of those things, but I personally prefer to concentrate the threat def. more so than the eternity(well, more like a "a very long time" than eternity) def., but I guess you can go with what you like. :)
The resolution of this discussion can be inserted in the ko page.