Sun Chu (孫楚; died 282) was a native of Zhongdu commandery (中都縣; in present-day Pingyao) in Shanxi; who when quite young wished to become a recluse, and said to Wang Ji (王濟), "I will wash my mouth with rocks, and pillow my head on the running stream."
"Oh," replied Sun, not the least taken aback, "I will use the rocks for tooth powder, and the stream to cleanse my ears."
Rising to high military command, he was received at an audience by the Emperor; but he absolutely refused to kneel, and would do no more than bow, alleging that a guardian of the Throne should never let himself be at a disadvantage.
Literally "gargle rock pillow stream", it refers to a sore-loser who refuses to back down ever after making a mistake and continues to defend it to the end regardless of how unlikely the argument is.
It may also be the origin of the ateji for the Japanese word sasuga, or "流石", whose actual meaning is unrelated.