The letter O is one of only a handful of letters in our alphabet whose shape hasn’t changed much throughout its entire history. We can be fairly sure that O’s earliest ancestor was a Phoenician letter, ayin, that was based on a drawing of a human eye (hence O’s circular shape) and was in turn descended from a similarly shaped Egyptian hieroglyph. In these ancient languages, however, O—or, at least, its eye-shaped ancestor—probably represented a consonant, and it took the Ancient Greeks to adopt it and use it to represent their letter omicron to transform our humble O into a vowel.

Nowadays, O is one of the most-frequently used letters of our alphabet, accounting for just over 7 percent of a standard page of text and just over 3 percent of all the words in a standard dictionary—including the 40 outstanding O words outlined here.

1. OBACERATE

Derived from a Latin word meaning “to contradict,” if you obacerate someone then you stop them from talking.

2. OBAMULATORY

Obambulation is the act of wandering around, and anyone (or anything) described as obambulatory is doing precisely that.

3. OB-AND-SOLLER

An ob-and-soller, according to the Oxford English Dictionary, is “a person who engages in scholastic disputation”—or, more loosely, a hair-splitting, pedantic nitpicker. The term was coined in 1678 by the English poet Samuel Butler, who based it on the older expression “obs and sols,” which was used to refer to the “objections and solutions” to a problem or issue being debated.

4. OBEQUITATE

To ride away on a horse.

5. O-BE-JOYFUL

Despite its religious overtones, o-be-joyful was 19th century slang for liquor, while an o-be-joyful works was a pub. And if you’ve had too much of that …

6. OBFUSCATED

… then you’ll be obfuscated—which literally means “overshadowed” or “placed into shade,” but was used as a euphemism for drunkenness in Victorian slang.

7. OBLATRANT

Derived from the Latin word for a dog’s bark, any written work described as oblatrant would rail against or condemn another work.

8. OBLIGURE

To obligure is to eat a great meal—while to obligurate is to spend time feasting or banqueting.

9. ODD-COME-SHORTLY

An 18th century dialect word meaning “someday” or “at some point in the future.”

10. OEILLADE

An old-fashioned word derived from the French word for “eye” for an amorous or knowing glance.

11. OFF-OX

Oxen are proverbially stubborn creatures, so an ox that’s having an off day must be particularly irritable—which explains why off-ox became a nickname for an unmanageable, bad-tempered man in 19th century American slang.

12. OFFMAGANDY

An old English dialect word for the choicest or most delicious foods.

13. OLG

As well as being another word for oppressive heat or humidity, you can use the Scots dialect word olg as a verb meaning “to spoil” or “to become slimy through decay.”

14. OLIGOGLOTTISM

The prefix oligo–, derived from a Greek word meaning “few” or “small,” is used to form opposites of words beginning with the prefix poly–, meaning “many.” So if a polyglot is someone who speaks a number of languages, then oligoglottism is a very limited knowledge of languages. Likewise an oligosyllabic word is one with very few syllables; an oligophagous creature is one with a very limited diet; and an oligopoly is a market in which there are only a limited number of vendors.

15. OMNIBENEVOLENT

Derived from Latin, the prefix omni– is used to mean “all” or “every,” as in omnidirectional or omnipresent. So someone who is omnibenevolent is infinitely or universally kind; someone who is omnidextrous is good at everything they turn their hand to; and someone who potentially or figuratively rules over the entire universe would be an omniarch. Likewise, if you’re an …

16. OMNILEGANT

… then you’re extremely well-read or familiar with a great amount of literature, while an omniloquent person is able to talk about any possible subject.

17. OMNIUM-GATHERUM

A half-Latin-half-English word (also spelled omnigatherum) for a random assortment of things, or an odd-job man or jack-of-all-trades.

18. ONEIROCRITIC

Oneirocriticism is the interpretation of dreams, and an oneirocritic is someone who does precisely that. Likewise …

19. ONEIRODYNIA

… is another word for a poor night’s sleep caused by, or worsened by, bad dreams or nightmares.

20. ONWEEDY

An old English dialect word used to describe something that will soon run out or will soon be finished.

21. OOFTISH

Derived from Yiddish expression gelt afn tish, literally meaning “money on the table,” ooftish or oof was slang for money or cash in late 19th century–mid 20th century English. Likewise, you could be oofless—or, in other words, poor or bankrupt.

22. OOGA-TOOGA

Derived from the local name of a type of sparse grass or weed that grows among corn, ooga-tooga is an old nickname from the far north of Scotland for the scanty hairs on top of a balding man’s head.

23. OOM

If something ooms, then it appears out of mist or darkness

24. OPHIDIOPHOBIA

Reportedly one of the commonest of all phobias, if you’re ophidiophobic then you’re scared of snakes. Other O-phobias include ochlophobia (the fear of mobs), ornithophobia (birds), oneirophobia (dreams or dreaming), optophobia (opening your eyes), ochophobia (vehicles), odontophobia (teeth or dentistry), and oikophobia (the hatred of going home).

25. OPISTHENAR

The medical name for the back of your hand.

26. OPSIMATH

An opsimath is someone who only begins to study or learn in old age, while opsimathy is learning or education acquired in later life. Opsigamy, similarly, is the act of getting married late in life, while an opsigamist is someone who does precisely that.

27. OPSOMANIAC

Someone who has an excessive craving or love of one particular food is an opsomaniac, while …

28. OPSONATION

… is a formal word for the catering or serving of food.

29. OPUNCTLY

If you arrive opunctly, then you arrive right on time.

30. ORPHAN-COLLAR

If the collar of your shirt doesn’t match the rest of it in color or fabric, then it’s an orphan-collar.

31. OTACOUSTICON

An alternative (and much better) word for an ear trumpet.

32. OUT-SWIFT

To out-swift, outspeed, or out-trot someone is to overtake them.

33. OUTRANCE

Derived from a French word essentially meaning “out of bounds,” outrance or oultrance is an old 15th century word for the greatest or furthest degree of something. That being said, you typically wouldn’t see outrance being used on its own—instead, it tends only to be used in phrases like to the outrance (meaning “to the very end”), to fight to the outrance (“to fight to the death”), or at outrance (“at the very last extremity”).

34. OUTRECUIDANCE

Another French-origin word, meaning excessive over-bearing arrogance or self-esteem.

35. OVERSLAUGH

As well as being an old name for a sandbank or sandbar (in which case it was probably originally a place name referring to a specific sandbank on the Hudson River near Albany, New York), you can also use overslaugh as a verb variously meaning “to stop the progress of,” “to forget to do something,” or “to pass someone over for promotion.”

36. OVERSPANG

An old Scots dialect word meaning “to leap over something.”

37. OVERTHWART

Take your pick from any of these: as a noun, an overthwart is a diagonal, transverse route or path, or the opposite point from where something is now, while your overthwart neighbor is the person who lives opposite you. As a verb, overthwart can be used to mean “to act in opposition,” “to lie across (something) so as to obstruct (someone),” and “to walk across or to pass something.” As an adjective, it means the same as “aslant,” “oblique,” or else “contentious” or “contrary.” And as a preposition or an adverb, it can be used to mean “on the far side of,” or “from side to side.”

38. OVERWAIST

If something is overwaist, then it’s submerged in water.

39. OWL-LIGHT

A 16th century nickname for twilight.

40. OWLGLASS

Owlglass is the English translation of the German surname Eulenspiegel, the name of a legendary jester and prankster in German folklore. It can be used simply as another name for a fool or buffoon, and as a verb meaning “to play practical jokes.”