There’s an old language myth that claims posh stands for “port out, starboard home.” According to the tale, the first posh people were wealthy cruise ship passengers who could afford to book two cabins on their holidays—one on the port side of the ship, the other on the starboard—to ensure that they had the most comfortable trips when they headed out and when they returned home.

It’s a neat story, but a fictitious one. In fact, posh is more likely derived from nothing more than an old 19th century slang word for either a showily overdressed dandy, or for basic coinage and cash. But the popular “port out starboard home” story makes posh a prime example of a backronym, a word mistakenly presumed to be an acronym. Likewise, golf—supposedly standing for “gentlemen only, ladies forbidden”—is another. Tips are paid, according to some, “to insure promptness.” And then there are the old stories about "fornication under consent of the king” and fertilizer being labelled “ship high in transit,” and even that most 21st century of words, bae, is sometimes said to stand for “before anyone else.”

But if those are all backronyms, then what about the genuine acronyms? Well, here are the stories and meanings behind 25 words, names and titles that you might not have realized actually stand for something.

1. AGA

Not the aga as in “Aga Khan,” this Aga is a type of cast-iron cooking range invented in Sweden in the early 1920s, which became popular in large country houses and middle class homes in the mid 20th century—so much so, in fact, that Aga saga is still a British slang expression for a genre of literature characterized by exaggerated stories set in rural middle class England. The name Aga stands for Aktiebolaget Gasaccumulator, or “The Gas Accumulator Company” in Swedish.

2. BASE JUMPING

A form of parachuting in which jumpers leap from fixed objects, base jumping started back in the 1980s. It takes its name from the four types of fixtures that you can jump from: building, antenna, span, or Earth.

3. CAPTCHA

The next time you’re asked to enter a practically illegible string of characters or numbers into a website to prove that you’re human, it’s worth remembering that Captcha stands for “completely automated public Turing Test to tell computers and humans apart.” (Although unsurprisingly the name was also deliberately coined to sound like “capture.”)

4. CARE PACKAGE

The first care packages—or rather, CARE packages—were put together in the aftermath of the Second World War with the aim of providing food relief to war-torn Europe. They were the work of what was then a newly formed humanitarian agency known as The Cooperative for Assistance and Relief Everywhere, founded in 1945.

5. COMECON

Not to be confused with ComicCon, Comecon—or the Council for Mutual Economic Assistance—was an economic organization founded in the 1940s that linked all of the Eastern Bloc nations of Eastern Europe. Led throughout its existence by the Soviet Union, Comecon was disbanded in 1991.

6. DERV

Or in other words, diesel oil for “diesel-engined road vehicles.”

7. E-FIT

Although it’s often misused as simply a synonym for “photofit,” technically the name E-fit refers only to the computer program used to produce composite pictures of police suspects based on people's descriptions. It stands for “electronic facial identification technique.”

8. GESTAPO

The Gestapo came into being in Nazi Germany in 1933. Its name is an acronym of Geheime Staatspolizei—literally meaning “secret state police.”

9. GIF

American computer scientist Steve Wilhite created the “graphics interchange format,” or gif, in 1987. (And the inventor thinks you should be pronouncing it “jiff,” not “giff.”)

10. GIGAFLOP

As a measure of the processing speed of computers, the “flop” of words like gigaflop and megaflop stands for “floating-point operations per second.”  Originally it was spelled gigaflops (which some people still prefer), but the -s was dropped to avoid thinking it was plural.

11. Gulag

The former Soviet labor camp's name was an acronym for glavnoye upravleniye lagerey, literally the Chief Administration for Camps.

12. HUMVEE

Like deejay and emcee, Humvee is one of a rare group of words formed by a vague attempt to pronounce a string of letters—in this case the acronym HMMWV, standing for “high-mobility multi-purpose wheeled vehicle.”

13. PAKISTAN

The name Pakistan is said to be derived from the Urdu and Persian word pak, meaning “pure.” But when the name was first coined in 1933, the independence activist Choudhry Rahmat Ali also suggested that it worked as an acronym of the five northern kingdoms of British India: Punjab, Afghania, Kashmir, Sindh and, giving it its final few letters, Baluchistan.

14. POG

If you grew up in the '90s, you probably played Pogs. But according to the OED, the name was an acronym for passion fruit, orange, guava, and was named after a drink in Maui that provided the lids for the first games.

15. and 16. RADAR and SONAR

Radar technology was developed in the lead-up to the Second World War. Its name was coined in the 1940s as an acronym of “radio detection and ranging,” and has since been used as a template for the names of other similar technologies, including sonar (“sound navigation and ranging”) and lidar (literally “light radar”).

17. SCUBA

When you’re scuba diving, you’re using “self-contained underwater breathing apparatus.”

18. SIM CARD

And the SIM card in your phone is really your “subscriber identification module” card.

19. SMART CAR

A division of the Daimler organization, the Smart Automobile company was founded in Germany in 1994. Originally known as the “Swatchmobile” (because the car was developed by the same company that makes Swatch watches), the name “Smart car” was chosen in the mid-1990s as an acronym of “Swatch Mercedes Art.”

20. SNAFU

A snafu is a mistake, or a general state of confusion or disarray. It was coined in the early 1940s, apparently by American troops during the Second World War, and according to the Oxford English Dictionary is “an expression conveying the common soldier’s laconic acceptance of the disorder of war and the ineptitude of his superiors”—namely, “situation normal, all f****d up.”

21. SOWETO

The Soweto suburb of Johannesburg, South Africa, is an acronym of “south-western townships.”

22., 23., and 24. TASER, LASER, and MASER

Taser stands for “Thomas A. Swift’s electric rifle,” but the notorious electroshock device was actually invented by an engineer named Jack Cover in the late 1960s. Cover decided to name his invention in honor of his childhood hero, Tom Swift, the fictitious star of a series of children’s sci-fi adventure novels. But chances are he also modelled it on laser (“light amplification by stimulated emission of radiation”), which in turn took its name from the even earlier maser technology (“microwave amplification by stimulated emission of radiation”).

25. ZIP CODE

Zip codes were introduced to the American postal service in 1963 as a means of speeding up the delivery of the mail by dividing the country into identifiable numerical zones. There is some disagreement as to whether the “zip” of zip code is an acronym or a backronym, but either way it’s said to stand for “zone improvement plan.”