truepenny

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.