If a palindrome is a word that reads the same backwards as forwards, then a semordnilap is a word that spells out a different word when read backwards, like stressed and desserts, or diaper and repaid. That definition makes the word semordnilap a semordnilap itself—but whereas most semordnilaps are little more than sheer coincidence, a word or name that is intentionally invented by reversing another existing word is properly called an ananym.

Words coined by reversing others aren’t quite as rare as they might seem. It’s a technique used to invent everything from place names, like Adanac in Canada and Adaven in Nevada, to first names: the Scots name Segna is thought to have been invented by (mostly) reversing the name Agnes, while Nevaeh, coined by reversing the word heaven, recently crept into the top 100 girls’ names in America. It’s also a popular source of brand names, like Oprah Winfrey’s Harpo Productions. Fiction writers too often call on ananyms when it comes to inventing characters and settings, like Samuel Butler’s Erewhon (a mangled reversal of nowhere) or Dylan Thomas’ Under Milk Wood (set in the fictional Welsh village of Llareggub, a none-too-subtle reversal of “bugger all”). And when a mysterious Hungarian aristocrat named Count Alucard turns up in New Orleans in the 1943 film Son of Dracula—well, you can guess what happens next.

Besides all the brand names and proper nouns, however, a handful of ananyms and semi-ananyms have backed their way into the dictionary—including the 10 explained here.

1. YOB

In 19th century English, back-slang was the name of a popular word-forming technique that created jokey replacements for everyday words by reversing their letters or sounds. So a fire was an “erif,” cabbage became “edgabac,” a policeman was a “namesclop,” and a birk was a house (derived from a reversal of “crib”). While many modern words have been suggested as originating from the back-slangers of Victorian England, the only one to definitely survive in current usage is yob.

2. YARG

Yarg is a cow’s-milk cheese made in Cornwall that is unique in that it’s wrapped in a layer of nettle leaves before being left to mature. The cheese’s recipe is credited to a local dairy farmer whose surname, Gray, was reversed to give the cheese its name.

3. MHO

If the ohm is a unit of electrical resistance, then its reverse, the mho, is a unit of electrical conductance; appropriately enough, while the Greek letter omega (Ω) is used to represent the ohm, an upside-down omega is used to represent the mho. Sadly the mho is not universally accepted in scientific literature, and the official SI unit of conductance is instead the siemens.

4. DARAF

Just like the mho and the ohm, the daraf is a unit of electrical elastance coined by reversing the name of the SI unit of electrical capacitance, the farad. The daraf too isn’t universally employed; its accepted equivalent is just called the “reciprocal farad.”

5. THERBLIG

In 1921, an American engineer named FB Gilbreth and his wife Lillian published a landmark report on workplace efficiency, now credited with introducing the very first time-and-motion study. By observing the movements of bricklayers, Gilbreth theorized that every physical operation carried out in a workplace could be divided into 16 basic movements: search, find, select, grasp, transport loaded, position, assemble, use, disassemble, inspect, pre-position, release, transport empty, rest for overcoming fatigue, unavoidable delay, and avoidable delay (later, researchers have added one or two more to the list). He called these basic divisions of action therbligs—a reversal (albeit a partial one) of his surname—and concluded that employers looking to get the best out of their workforce should, in Lillian's words, “study your man, determine what product he can best make, give him the working conditions, machines and materials that are best suited to him,” and in that way, “you may expect success.”

6. YAROOH

According to the Oxford English Dictionary, yarooh is “a humorous stylized representation of a cry of pain.” It’s credited to the English writer Charles Hamilton, who, under the pen name Frank Richards, created the word for his popular Billy Bunter comic strip in 1909. As a cry of anguish, as opposed to joy or excitement, Hamilton apparently came up with the spelling yarooh by reversing the letters of hooray.

7. ATLED

Introduced in the mid-19th century, atled is the entirely appropriate name of an inverted form, ∇, of the triangular Greek letter delta, Δ, that’s used in some branches of mathematics to represent gradient. Like the mho and the daraf before it, however, the name atled isn’t universally used—the more usual name for this symbol is nabla, the Greek name of a type of harp shaped like an inverted triangle.

8. KAYO

In 1920s slang, kayo was used as a humorous replacement for “OK,” coined by reversing the sounds of the two letters rather than the letters of the word okay itself (it was possibly influenced by the boxing KO, a term that was coming into common usage at the exact same time).

9. SKOOB

In the mid-1960s, the British conceptual artist John Latham coined the word skoob to refer to a pile of books destined to be destroyed. According to the Oxford English Dictionary, Latham’s skoob was intended to be “a gesture against the proliferation and undue veneration of the printed word,” but in introducing the term he gave us a general word for “the ceremonial burning of a book or books.”

10. ALLEREDNIC

A term coined by Oxford professor of sociology Jonathan Gershuny, Allerednic syndrome is essentially the reversal of the Cinderella story. As such it describes to a successful woman who marries an equally successful man and in doing so is forced to give up her career and status to act as a full-time mother or housewife. Or, as Cherie Booth, wife of former British Prime Minister Tony Blair, once put it, “You know the story: the prince marries the princess, and turns her into a scullery maid.”