A Hand of Glory is the dried and pickled hand of a hanged man, often specified as being the left (Latin: sinister*) hand, or, if the person was hanged for murder, the hand that "did the deed."
*In Latin, sinister originally meant "left" or "on the left side," but it developed negative connotations of "unlucky," "unfavorable," or even "malicious" due to superstitions and religious beliefs associating the left side with misfortune and the demonic. The word shares an etymological root with dexter ("right"), from which the word "dexterity" is derived, contrasting the skilled and auspicious right with the unlucky and awkward left.