MONSTRUM
[noun]
Latin: a sign or portent that disrupts the natural order as evidence of divine displeasure. The word monstrumis usually assumed to derive, as Cicero says, from the verb monstro, “show” (compare English “demonstrate”), but according to Varro it comes from moneo, “warn.” Because a sign must be startling or deviant to have an impact, monstrum came to mean “unnatural event” or “a malfunctioning of nature.” Suetonius mentioned that “a monstrum is contrary to nature [or exceeds the nature] we are familiar with, like a snake with feet or a bird with four wings.” The Greek equivalent was teras. The English word “monster” derived from the negative sense of the word.
(via thatguyhasabeardandmoxie)