Game of Thrones is known for its linguistic inventiveness. The TV adaptation of George RR Martin’s fantasy cycle has gone way further than the original novels ever did, with linguist David J Peterson fleshing out the languages of Essos and Westeros, Dothraki and Valyrian, from one or two phrases into grammatically coherent “conlangs” or constructed languages.

The latest piece of vocabulary to come out of the show has nothing to do with him, however. In fact, it wasn’t purposely designed by anyone. I’m tempted, because of the genre we’re dealing with, to call it an epic fail. But it’s probably not as bad as leaving a Starbucks cup in shot. And it’s actually pretty fascinating.

A crucial line during one battle scene in a recent episode was “She can’t see us!”, delivered in light Geordie by Irish actor Liam Cunningham. In the dubbed Spanish version it came out as “Sicansíos!” (OK, let’s get this right: “¡Sicansíos!”). The problem is, there’s no such word. The accurate translation would have been no puede vernos. Perhaps viewers thought it was a spot of Valyrian. That must be what the voice actors assumed, or at least wanted their bosses to believe after having failed to decode Cunningham’s accent.

Anyway, it wasn’t long before viewers picked up on the mistake, with sicansíos rapidly becoming the most famous bit of nonsense since covfefe. What’s interesting about it from a linguistic point of view is how it takes the original phrase and stuffs it through an aural filter, adapting the sounds of English to ones Spanish speakers are used to. This is most obvious in the disappearance of the “sh” of “she”. European Spanish doesn’t naturally have this sound, but its version of “s” can sometimes resemble the English “sh” – hence the substitution in sicansíos.

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This process – of forcing the square peg of a word from one language into the round hole of another – isn’t all that unusual. It’s happened throughout history when languages have come into contact – often through war or trade or cultural exchange. Unlike sicansíos, these foreign words often accompany favoured products or useful concepts, and end up being permanently borrowed. Not only that, but they can get squeezed through a sort of semantic filter, as well as an aural one.

Let me explain. There’s a word in English, crayfish, that refers not to a fish but a relative of the lobster. We got that word from the Old French crevice (in modern French it’s écrevisse), which in turn came from Old High German krebiz, meaning crab. What happened to crevice after being taken up in English was that it changed a bit in sound terms, with the stress shifting from the second to the first syllable. But it also got interpreted slightly differently too. The meaningless -ice ending felt like it ought to mean something. And since this was an animal that lived in water, a fish is what it became.

This is one type of what linguists call a folk, or popular etymology. People adapt a word according to the sounds and meanings they’re used to, departing from the original in the process. There are loads of entertaining examples of it (the ones in this article come courtesy of historical linguists Lyle Campbell and Larry Trask, and the Oxford Dictionary of English Etymology).

Take the English “country dance”, which in the 18th century became so popular it was borrowed into French, where it was pronounced contre-danse. Contre means against, or opposite, which fitted very well with a line of men facing a line of women, and that’s how it was interpreted. With its air of continental sophistication, the French phrase was eventually borrowed back into English, leading some to believe that country dance was a corruption of contre-danse, and not the other way around.

Benzoin is a rich incense made from the resin of a tree that grows in Indonesia. It’s also known as gum benjamin, which is a further Anglicisation of something quite alien-looking. But where does the word benzoin come from? The Arabs who traded this substance called it “frankincense from Java”, or luban jawi. In that phrase you can already see the ban jawi element that became benzoin. But what happened to the lu? Italian is what happened. Lu sounds a bit like the Italian definite article, lo. So luban jawi was interpreted by 16th-century Italian merchants as lo benzoi, “the benzoi”. As a result only the second bit became the noun in the European languages that borrowed it.

The most bizarre folk etymology of all was probably a one-off, just like sicansíos – although it had long-lasting consequences for at least one individual, if we are to believe the story. During the US occupation that followed Spanish rule in the Philippines, one Filipino father was said to have named his son Ababís, after America’s patron saint (san in Spanish). The thing is, the US doesn’t have a patron saint. All becomes clear if you think of how a phrase that was common currency among American occupiers would have sounded to a Spanish-attuned Filipino. In that context, it’s just a short step from “son of a bitch” to San Ababís, and a pretty terrible misunderstanding.

• David Shariatmadari is an editor and writer for the Guardian. His book Don’t Believe a Word: The Surprising Truth About Language (Weidenfeld & Nicholson) is out in August