molly-guard

/moleegard/ , n. [University of Illinois] A shield to prevent tripping of
some Big Red Switch by clumsy or ignorant hands. Originally used of the
plexiglass covers improvised for the BRS on an IBM 4341 after a programmer's
toddler daughter (named Molly) frobbed it twice in one day. Later
generalized to covers over stop/reset switches on disk drives and networking
equipment. In hardware catalogues, you'll see the much less interesting
description guarded button.