This is the forum for helping you out if you're stuck or if you want to discuss the nitty gritty details of the dungeons within Mount Grimrock. Warning: forum contains spoilers!
It's the key to the code found in the Archives, on a sign in Twigroot Forest, and at the very end of one of the game's endings (encoded with an additional cypher there).
SpoilerShow
UHU means move forward. AR means move backwards. LAM means move down. TE means move right. E means once. NA means twice. KO means thrice. FAAM means rotate clockwise. PALA means rotate counterclockwise.