When the lexicographer Dr. Samuel Johnson put together his Dictionary of the English Language in 1755, there weren't a lot of words that started with X; he even included a disclaimer at the bottom of page 2308 that read, “X is a letter which though found in Saxon words, begins no word in the English language.” Noah Webster went one better when he published his Compendious Dictionary in 1806 that included a single X-word, xebec, defined as “a small three-masted vessel in the Mediterranean Sea.” Although, by the time he compiled his landmark American Dictionary in 1828, that total had risen to 13.

X has never been a common initial letter in English, and even with today’s enormous vocabulary you can still only expect around 0.02 percent of the words in a dictionary to be listed under it. But why not try boosting your vocabulary with these 40 words that start with X.

1. X

On its own, the letter X is listed in the Oxford English Dictionary as a verb meaning “to cross out a single letter of type.” X. X. in Victorian slang meant “double-excellent,” while X. X. X. described anything that was “treble excellent.”

2. XANTHIPPE

Xanthippe was the name of Socrates’ wife, who, thanks to a number of Ancient Greek caricatures, had a reputation for henpecking, overbearing behavior. Consequently her name can be used as a byword for any ill-tempered or cantankerous woman or wife—as used in Shakespeare’s Taming of the Shrew.

3. XANTHOCOMIC

Jag_cz/iStock via Getty Images

Xanthos was the Ancient Greek word for yellow, and as such is the root of a number of mainly scientific words referring to yellow-colored things. So, if you’re xanthocomic, you have yellow hair; if you’re xanthocroic you have fair hair and pale skin; and if you’re xanthodontous, you have yellow teeth.

4. X-CATCHER

In old naval slang, an X-catcher or X-chaser was someone who was good at math—literally someone good at working out the value of x.

5. X-DIVISION

Victorian slang for criminals or pickpockets, or people who make a living by some underhand means.

6. X-DOUBLE-MINUS

BrianAJackson/iStock via Getty Images

1960s slang for something really, really terrible.

7. XENAGOGUE

Derived from the same root as xenophobia, a xenagogue is someone whose job it is to conduct strangers or to act as a guide while…

8. XENAGOGY

… a xenagogy is a guidebook.

9. XENIAL

Rawpixel/iStock via Getty Images

The adjective xenial is used to describe a friendly relationship between two parties, in particular between a hospitable host and his or her guests, or diplomatically between two countries.

10. XENIATROPHOBIA

Don’t like going to see doctors you don’t know? Then you’re xeniatrophobic.

11. XENIUM

A xenium is a gift or offering given to a stranger, which in its native Ancient Greece would once have been a lavish feast or a refreshing spread of food and fruit. In the 19th century art world, however, xenium came to refer to a still-life painting depicting something like a extravagant display of food or a bowl of fruit.

12. XENIZATION

Sushiman/iStock via Getty Images

A 19th century word meaning “the act of traveling as a stranger.”

13. XENOCRACY

A government formed by foreigners or outsiders is a xenocracy. A member of one is a xenocrat.

14. XENODOCHEIONOLOGY

Defined as “the lore of hotels and inns” by Merriam-Webster.

15. XENODOCHIUM

Rawpixel/iStock via Getty Images

A guesthouse or hostel, or any similar stopping place for travelers or pilgrims.

16. XENODOCHY

A 17th century word for hospitality. If you’re xenodochial then you like to entertain strangers.

17. XENOGLOSSY

The ability to speak a language that you’ve apparently never learnt.

18. XENOLOGY

BWFolsom/iStock via Getty Images

The scientific study of extraterrestrial phenomena is xenology. The study of extraterrestrial life forms is xenobiology.

19. XENOMANIA

The opposite of xenophobia is xenomania or xenophilia, namely an intense enthusiasm or fondness for anything or anyone foreign.

20. XENOMORPH

Something unusually or irregularly shaped is a xenomorph—which is why it’s become another name for the eponymous creature in the Alien film franchise.

21. XENOTRANSPLANTATION

monkeybusinessimages/iStock via Getty Images

Transplanting organic matter from a non-human into a human (like a pig’s heart valve into a human heart) is called xenotransplantation. Whatever it is that’s transplanted is called the xenograft.

22. XERIC

An ecological term used to describe anywhere extremely dry or arid. If it’s xerothermic, then it’s both dry and hot.

23. XERISCAPE

If you live in a xeric area, then you’ll have to xeriscape your garden. It’s the deliberate use of plants that need relatively little moisture or irrigation to landscape an arid location.

24. XEROCHILIA

dragana991/iStock via Getty Images

The medical name for having dry lips. Having a dry mouth is xerostomia.

25. XEROCOPY

A xerographic copy of a document—or, to put it another way, a photocopy.

26. XEROPHAGY

The eating of dry food is xerophagy. It mightn’t sound like it, but it was originally a religious term.

27. XESTURGY

The proper name for the process of polishing.

28. XILINOUS

popovaphoto/iStock via Getty Images

Something described as xilinous resembles or feels like cotton …

29. XIPHOID

… while something described as xiphoid resembles a sword.

30. XOANON

Derived from the Greek for “carve” or “scrape,” a xoanon is a carved idol of a deity.

31. XTAL

de-kay/iStock via Getty Images

An abbreviation of “crystal,” according to the OED.

32. XYLOGRAPHER

A 19th century word for a wood engraver.

33. XYLOID

Why say that something is “woody” when you can say that it’s xyloid?

34. XYLOPOLIST

Javier Díez/iStock via Getty Images

A 17th century formal name for a timber merchant.

35. XYLOTOMOUS

Describes anything or anyone particularly good at wood-cutting or wood-boring.

36. XYRESIC

Means “razor-sharp.”

37. XYROPHOBIA

Comstock Images/iStock via Getty Images

The fear of being close to or touching sharp implements.

38. XYLANTHRAX

Nowhere near as nasty as it sounds, this is just an old name for what we now call charcoal.

39. XYSTUS

A type of covered walkway or portico.

40. X.Y.Z.

Late 19th century slang for a journalist who takes on any work going, or else 18th century slang for a dandyish or “exquisite” young man.