In one of my frequent daydreams in which I imagine a parallel world where I'm unfeasibly rich and powerful, I've invented a bath overflow warning system called the Liquobeep. It hangs over the side of the bath and emits a noise when the water reaches the correct level; it's hailed as the most brilliantly simple home gadget of the decade, and is immediately repurposed for sinks, pools, drains, rivers and reservoirs. I experience a warm glow whenever I hear people say "I need to do a Liquobeep" or "You should have Liquobeeped it", and enormous pride when Liquobeep eventually comes to mean any act you perform to ward off potential danger or peril. At which point my trademark slips into the public domain, my business empire crashes, and I snap out of the daydream, covered in sweat, while the beeping of a reversing lorry sounds faintly in the distance.

Things like this do happen. It's called genericide, and successful companies and their lawyers are waging a constant battle against it.

Washington Post columnist Gene Weingarten recently and unexpectedly found himself involved in one such battle after light-heartedly suggesting to his readers that they might feel more American if they "put on a Stetson". Lawyers for the John B Stetson Company were quick to contact Weingarten and insist that he refrain from using the word "Stetson" as a synonym for "hat", and to always write it as "Stetson®". Weingarten reacted grumpily on his blog ("Stetson® hats suck"), but follow-up correspondence he received from trademark lawyers explained that one of the main strategies to fight the generic usage of such words is to be seen to be pro-active; the company has to be able to demonstrate that it cares about its trademark. The paperwork that's now on file concerning the mentions of the Stetson® hat in the Washington Post may well end up being valuable in court.

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Genericide is the cruellest irony. A firm might come up with a brilliant marketing strategy that successfully pushes a product to the forefront of its sector, but if its trademark becomes so colloquial that it starts to mean the entire product category, it can kill it – and kill profits as other businesses wade in.

History is littered with moments when companies and inventors, unwise to the dangers, began to have trouble controlling their trademarks; Hoover is one of the most obvious examples to the British, but marks such as zipper and yo-yo lost their status completely decades ago, and it's continuing to happen, netbook and pilates being two more recent examples.

You might think, well, it's only a name – but it's far more than that. "Companies invest huge sums in new product development and building their brands," says Wendy Lomax, Professor of Brand Marketing at Kingston University. "If Guinness are spending £10m on a single advert, the last thing they want is for people to be using the word Guinness to mean any kind of stout."

The problem stems from the subtle ways in which language develops. It's instinctive for us to pluralise product names in everyday conversation (Oreos, Jet Skis) or turn them into verbs (to photoshop, to tarmac). But by doing so we begin to erode the trademark. Companies can, from the outset, encourage us to use an alternative generic name; sometimes this works (Nintendo pushing the term "games console"), sometimes it almost works (Xerox's fondness for the term "photocopying"), and sometimes it fails miserably (who has ever referred to the once-trademarked trampoline as a "rebound tumbler"?)

Reinforcing the brand can make for tortuous English (see box left, particularly the Xerox example), but for the company, it's a necessary evil. Alongside savvy marketing and awareness of the pitfalls of genericide stands a formidable legal machine of the kind that admonished Weingarten. "Until a few years ago I acted for Rollerblade," recalls Nigel Jennings, senior partner at Kilburn & Strode, "and whenever we were informed by a press cuttings agency that someone had referred to having rollerblades or going rollerblading, they would receive a letter from me. I sent hundreds."

But can this kind of action work in the internet age, where language is used in a carefree fashion and the perpetrators are hard to track down? "Things have certainly changed," says Jennings. "If something becomes generic because everyone ignored your requests, well, that's just fact. You're like King Canute, you've failed."

One of the most regularly used verbs in the 21st century that shouldn't be used as a verb at all is "to google". When we refer to "googling" for products and services, we generally mean visiting google.com and typing in a query – but it could equally mean searching the internet by other means, too. There was a point where Larry Page and Sergey Brin, Google's founders, would have embraced the idea of their brand into a verb; indeed, the first reference found to "googling" occurs within something posted online by Page himself on 8 July 1998. And, as Nigel Jennings notes, that kind of excitement is understandable. "I've come across a number of clients that thought generic use was a wonderful thing and, in fact, I lost one trademark application after evidence showed that my client had been using the term generically."

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These days, Google are wiser and more aggressive, with occasional flurries of letters requesting publications not to refer to "googling". But will it ever manage to stop us using the term in everyday speech? It's unlikely. Unless, of course, it begins to lose its 70 per cent market share. In the meantime, happy googling – or, as the dictionary more correctly states, "using the Google search engine".

Tarnished trademarks

Escalator

Following a trademark application by a Mr Charles Seeberger in 1900, competitors of Otis, manufacturers of the Escalator, were forced to refer to their products as motorstairs or electric stairways. But everything changed in 1950 with the court case of Haughton Elevator Co v Seeberger. The judge ruled the term had become generic, mainly through Otis's negligence; the company had used the word "escalator" alongside the generic term "elevator" in advertising and, crucially, hadn't capitalised the word "Escalator" correctly in the original trademark application, using "ESCALATOR" instead.

Band-Aid

In many countries the term is used generically for sticking plasters, and in everyday speech to mean a temporary fix for something. But Band-Aid has continued to crusade against genericisation. A song used in one American television advert for Band-Aid, penned by Barry Manilow and sung by various children with minor skin abrasions, originally used the phrase "I am stuck on Band Aid, 'cause Band-Aid's stuck on me"; in the 1980s this was changed to the more tongue-twisting "I am stuck on Band-Aid Brand, 'cause Band-Aid's stuck on me".

Aspirin

A century ago, German pharmaceutical company Bayer achieved success with their trademarked "Heroin" and "Aspirin" drugs. Heroin's "non-habit forming" properties saw it become a popular cure for respiratory ailments, while Bayer's deliberately awkward generic name for Aspirin (monoacetic acid ester of salicylic acid) saw the brand name slip into common parlance. But during the Spanish flu epidemic hundreds of varieties of aspirin hit the shelves, and Bayer's efforts to protect the trademark failed. At the end of the war, the Treaty of Versailles revoked the trademarks for both aspirin and heroin in France, Russia, the UK and US.

Xerox

In the early 1970s, Xerox's colossal market share of photocopiers ensured that "xeroxing" became part of office vocabulary. Xerox saw trouble looming, and initiated PR campaigns to persuade the public to use the verb "to photocopy" instead. In 1975 an anti-trust suit forced Xerox to license its patents and its market share fell dramatically, but it continues to campaign against abuse of its trademark – despite it appearing in many dictionaries. "You cannot xerox a document," read one advertisement, "but you can copy it on a Xerox brand copying machine."