"That undiscovered country . . . " Shakespeare, from Hamlet, Act III, Scene 1: "The undiscover'd country from whose bourn / No traveler returns . . . "; Hamlet's line refers to death as "the undiscovered country."
limb i.e., "limb of Satan," a phrase meaning "imp" or "devil" (metaphorically, an arm or leg of Satan, doing the devil's work), commonly used as a euphemism.
