One of the metaphorical names for the game of go; literally "hand talk", used in both Chinese and Japanese.
John Fairbairn It's a Chinese term. The locus classicus is the The "New Account of the Tales of the World", a 5th century work, which says Zhi Dun (early 4th c.) was responsible for calling go "hand talk" (shou tan). Zhi was one of the cultivated clergy who practised "pure conversation" (qing tan) with the aristocracy in the Eastern Jin era. The same book says Wang Zhonglang, a high official of the same era was the originator of the phrase "sitting in reclusion" (zuo yin) to describe go. For wangyou (= boyu) see my articles on the MSO site. The Chinese have used these terms extensively. (A second copy of the Ming classic Zuoyin Yipu of 1609 has just come to light, incidentally.) Japan has borrowed much from China.
Other names for Go are given in the RGG FAQ, Part 1, Section 4.
HolIgor: A question. The first character is "hand" (SHU,te), isn't it? And the second one is "dan" as in step, dan. Right?
Bob McGuigan: the dan in shudan as above is 談, which has the meaning of talk, conversation, story telling, etc. The dan as step or grade is 段. In shudan using this dan. as in 手段 can be found in go books, where it means measure, means, way.
exswoo: You bring up an interesting mistake. The shudan you're thinking about is a different one (手段） that means "plan/strategy". The shudan that is meant to refer to go is 手談, which literally means hand talk or hand discussion. This is meant to mean "No words are needed when playing go."
There are two other nicknames for Go as well.
Yuugen(幽玄):Lit. mystery. As in "There is more to Go than meets the eye."
Bouyuu(忘憂):Lit: Forgetting Sorrow. As in "Go is so much fun that you will forget your troubles."
It's most likely that these names were chosen for its pun-like qualities. You already mentioned the one for Shudan, and for the other two I just mentioned, Yuu (遊) could also mean "Play/Game", so Yuugen would become "The illusionary game", and Bouyuu could be "The game that will make you forget your sorrow".
John Fairbairn The yugen comment is not really accurate but you need to get into Daoism to understand that one. The Daodejing will explain a few famous go allusions if you really want to go into the topic, not least the Gengen Gokyo/Xuanxuan Qijing title.
Edited by Charles Matthews