E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Hamlet says to the Ghost, Art thou there, Truepenny? Then to his comrades, You hear this fellow in the cellarage? (i. 5). And again, Well said, old mole; canst work? Truepenny means earth-borer or mole (Greek, trupanon, trupao, to bore or perforate), an excellent word to apply to a ghost boring through the cellarage to get to the place of purgatory before cock-crow. Miners use the word for a run of metal or metallic earth, which indicates the presence and direction of a lode.