Johnson in his 1755 Dictionary defines a charnel house as "The place under churches
where the bones of the dead are reposited" and a vault as simply "a repository for
the dead." By the latter Victor Frankenstein probably means to distinguish a mausoleum.
Body-snatching or grave-robbing, a means of supplying cadavers for medical experiments
and instruction, was a source of great anxiety in the eighteenth and nineteenth centuries.
It was, of course, a criminal activity.