Q: An “omen” can be “auspicious,” but something that’s “ominous” can’t be. Any insight about this surprising divergence?
A: An “omen” has always been neutral—it can be good news or bad—but something that’s “ominous” is a bummer. In fact, by definition “ominous” means inauspicious.
How did this come to be? Blame the Romans.
In classical Latin, an ōmen was “something that foreshadows an event or the outcome of an event,” according to the Oxford English Dictionary. And ōminōsus meant “inauspicious, portentous.”
When adopted into English in the late 16th century, the two words retained their Latin meanings—one neutral, the other negative.
“Omen,” first recorded in 1582, was (and still is) a neutral word for a prophetic sign. Here’s the OED’s definition: “An event or phenomenon regarded as a portent of good or evil; a prophetic sign, an augury.”
Oxford’s most recent example is positive: “Unlike lots of people I like spiders. They have always been an omen of luck to me.” (From the Weekly News, Glasgow, 1989.)
Yet “ominous,” first recorded in 1589, has always been unequivocally negative. There’s nothing good in the OED’s earliest definition: “Of ill omen, inauspicious; indicative or suggestive of future misfortune.”
This is still among its meanings, as shown in a modern OED example: “The ominous prospects of war could not dampen the enthusiasm of Karen Horney and her group for their new undertaking.” (From Susan Quinn’s A Mind of Her Own: The Life of Karen Horney, 1988.)
Within a few years of its first appearance, “ominous” took on wider negative senses unrelated to prophecy.
Oxford has citations beginning in 1593 for the word used to mean “menacing,” “awful,” or “unsettling” in reference to an appearance, a sound, an atmosphere, and so on.
The word is used this way even now, as in this OED citation: “There was an ominous, slow-motion replay of McVeigh’s ‘perp walk’ intercut with victims in agony.” (From the New York Times Magazine, June 2001.)
Only rarely, from the 1590s to the 1670s, has “ominous” ever been used in a positive sense, a usage the OED says is now obsolete.
We can’t explain why “omen” can be good or bad but “ominous” is only bad.
There’s no clue in Latin, according to the OED, which says the etymology of ōmen is unknown.
The American Heritage Dictionary of Indo-European Roots says the ō– of ōmen comes from a pre-historic Indo-European root meaning “to believe, hold as true.” But this doesn’t explain the different characters of “omen” and “ominous.”
We do know how “auspice” and “auspicious” developed. It all started with a word from Roman history, auspex, a contraction of avispex (a watcher of birds, from avis, bird, and –spex, an observer).
In Roman times, the OED says, an auspex was “one who observed the flight of birds, to take omens thence for the guidance of affairs.” Consequently, it also meant “a director, protector; and esp. the person who superintended marriage ceremonies.”
(The word “auspex” has been used in English only in reference to ancient Rome. In ordinary English, such a person is an “augur,” a word also derived from the Latin avis and one that we wrote about in 2011.)
In Latin, the word for what the auspex did—the divination or foretelling—was auspicium. And auspicium, the OED explains, gave French the noun auspice in the 14th century.
“Auspice” came into English from French in the 1530s, when it was used in the old Roman way. Here’s the OED’s earliest sense of the word: “An observation of birds for the purpose of obtaining omens; a sign or token given by birds.”
By the mid-17th century “auspice” was used in a more general and more positive way: “Any divine or prophetic token; prognostic, premonition; esp. indication of a happy future.”
Oxford’s earliest citation is a reference to “happy auspices” (1660), and the latest is to “fairest auspices” (1885).
The sense in which we use the word today—usually in the plural—came along in the early 1600s.
This meaning, which is entirely positive, is defined in the OED as a “propitious influence” or “patronage,” especially in the phrase “under the auspices of.”
So it’s no surprise that since its beginnings in the early 1600s the adjective, “auspicious,” has almost always meant of good omen, propitious, or favored by fortune.
We’ll close with a couple of quotes from Shakespeare, who knew a thing or two about portents.
“Thou ominous and fearful owl of death, / Our nation’s terror and their bloody scourge!” (King Henry VI, Part 1, circa 1591.)
“Then go thou forth; / And fortune play upon thy prosperous helm, / As thy auspicious mistress!” (All’s Well That Ends Well, c. 1605.)
from Grammarphobia http://www.grammarphobia.com/blog/2016/03/omen-ominous.html