The word allegory is derived from the words “all” and “gory.” Nobody has the slightest of ideas as to why there is an “e” in the word. It was likely some elitist aesthete’s idea of linguistic decoration.
The word allegory is something of an anachronism (at least until The Words Project has a go at the word anachronism) in that it uses a definition of the word all that is no longer in use. The now disused, historical definition of all that is used in allegory is everything or everyone, where as, in its current usage, all means the good life.
Allegory, thus, is an noun meaning an act or acts that is/are all (i.e., completely) gory. For example, the acts of a serial killer who devotes his every waking minute to killing people in the most horrific way imaginable, and often in ways that most of us fortunately can’t imagine, and then chopping up the bodies could be referred to as allegory.