Susan Stryker said this quote

“ Monster” is derived from the Latin noun monstrum, “divine portent,” itself formed on the root of the verb monere, “to warn.” It came to refer to living things of anomalous shape or structure, or to fabulous creatures like the sphinx who were composed of strikingly incongruous parts, because the ancients considered the appearance of such beings to be a sign of some impending supernatural event. Monsters, like angels, functioned as messengers and heralds of the extraordinary. They served to announce impending revelation, saying, in effect, “Pay attention; something of profound importance is happening. ”