Hamlet: . . . Give me one poor request. Horatio: What is't, my lord? we will. Hamlet: Never make known what you have seen to-night. . . .Indeed, upon my sword, indeed. Ghost: [Beneath] Swear. Hamlet: Ah, ha, boy! say'st thou so? art thou there, truepenny? Come on—you hear this fellow in the cellarage— Consent to swear.
Source: wiktionary