An omen is a sign or portent about some future happening. It might be a good omen or it might be a bad omen — the word “omen” is neutral. But if “omen” is neutral, why does “ominous,” which is simply something foretold by an omen, always have a negative connotation?
Whatever the reason, this distinction goes all the way back to the Latin roots of both words. “Omen” was taken directly from Latin, both spelling and meaning. And “ominous” comes from the Latin “ominosus,” which also shared our meaning: inauspicious. In spite of being Latin, and available for ages, “omen” and “ominous” didn’t enter English until the late 1500s.
Nobody really knows why “omen” has always been neutral and “ominous” (or “ominosus”) negative. The word most often used in defining “ominous” is “inauspicious”, which is actually very closely related. Back in ancient Rome, there was a person called an “auspex” whose job was to watch birds flying around and figure out what omens could be discerned from the ways they were flying (I know, but there are strange jobs nowadays too). The Latin word for the activities of the auspex was “auspicium,” which made it into French as “auspice” in the 1300s. By the 1530s “auspice” arrived in English, where, believe it or not, originally meant the same thing as it had in Rome; watching birds for signs of omens. But as far as I could find out, it was never really a job in England.
By the 1600s “auspice” was being used in a more general way to mean any foreshadowing of the future (no birds required), and it had acquired a positive implication. It was a sign of something good in the future. The adjective form, “auspicious,” has kept that same positive connotation. If something is “auspicious,” it bodes well.
Wherever the negative and positive connotations came from originally, they’ve shown no sign of changing any time soon (or not soon, for that matter). It’s possible that because we have both “auspicious” and “ominous,” we’ve already got the bases covered and don’t need to change anything. Since “omen” is a shorter and handier word, it’s nearly as easy to pair it with “good” or “bad” to distinguish whether we’re talking about an auspicious or ominous omen. Who knows. In any case, these are fascinating examples of fairly complex words that have remained completely unchanged for a very long time. You might even think that some auspex long ago foretold the whole affair — but come on, that kind of speculation is for the birds.
