When trademarks cross over into the everyday news — as in the recent case of a company filing a US trademark application in an attempt to register MH 17 as a trademark, the flight number of the downed Malaysia Airlines plane – it’s usually on account of someone trying to register and reserve use of a name or a phrase that’s entered the popular consciousness. Sometimes it’s something that originated with them, sometimes not – witness the men who tried to claim a trademark to the word “Linsanity” several years ago when basketball player Jeremy Lin was all the rage.

Let’s take a step back and look at what exactly the definition and purpose of a trademark is, before talking about what happens when people attempt to trademark popular names and phrases.

A trademark is intended to be a unique identifier of origin. It’s designed to protect both the purchasing public (whether they’re purchasing goods or services) and businesses themselves, by providing a sure way of knowing that you are indeed getting the genuine article. Consumers are protected from being misled by, for instance, similarly (or same) named businesses offering a subpar product, and businesses have less worry of losing potential customers to imposters.

The words “unique” and “identifier” are key in defining a trademark – and in attaining one. In order to be considered trademarkable, a name, phrase, or logo needs to be associated with just one entity.  Since one inherent purpose of a trademark is to prevent confusion as to origin, if more than one person or company can be associated with a name or phrase, it’s extremely difficult – or impossible – to prove that it’s a unique identifier.

That’s the underlying reason that a word or phrase making the rounds in the news is not likely to ever be approved for a trademark. In the case of Malaysia Airlines flight MH 17, the flight number “MH 17” has entered the public domain as a shorthand signifier for the event. It’s used by media and news outlets regularly, and there’s no way that it can now be claimed exclusively for use by one company just on the basis of a trademark filing.

Apart from the “origin” question, there’s also the question of “meaning” in a trademark. That is, if a word of phrase has acquired a distinct meaning in and of itself, beyond that word or phrase itself, it’s not possible to trademark it after the fact. In other words, on paper – before the events of the crash – “MH 17” had no other meaning. It’s just some letters and numbers – and prior to the crash, had someone attempted to trademark “MH 17” for a product or service, it likely would have been acceptable.

As soon as the crash occurred, though, that particular combination of letters and numbers attained a  meaning attached to the incident itself. That meaning became widespread, common vernacular – thus forgoing its ability to be trademarked.

There is a historical and legal precedent for these situations – and their outcomes. One such case was “Boston Strong,” after the Boston Marathon bombing. A t-shirt company and an individual attempted to trademark the phrase, which gained popular usage as a term of solidarity in the aftermath of the tragedy. As a phrase that was already turning up everywhere – from hats to hashtags to the Big Green Monster at Fenway Park – there was no legal basis for assigning the trademark to any one person, company, or organization.

What about cases where a trademark already exists for something that enters the public conversation in response to a major event? What if, hypothetically, a gym or other company in Boston had trademarked the phrase “Boston Strong” years ago? Let’s go back to two underlying issues of importance in trademark law: the matter of “use in commerce,” and the issue of “confusion” as discussed above.

An existing trademark for “Boston Strong” would not have been able to stop the use of the phrase as the rallying cry that it became – and it’s unlikely that a business owner would have complained, anyway. The trademark would become important once other companies began creating t-shirts or offering any other type of merchandise or service for sale that used the phrase. In that case, there may have been a legitimate trademark claim by the holder, as that trademark protects exclusive use in commerce.

A more legal gray area is the issue of “confusion.” Similar or identical trademarks are allowable so long as the usage is far enough apart that there’s no chance of confusion – for instance, vastly different industries, products, or services. So, in this hypothetical situation with an already existing “Boston Strong” trademark, a new trademark applicant might attempt to claim that the usage is far enough from the original that there’s no chance of confusion. But again, the fact that the phrase had already entered common public usage would preclude any claim of ownership over its meaning in relation to the Boston Marathon.

Other popular news stories can involve aspects that are able to be trademarked – when they involve one single concrete origin to which a word or phrase can actually be traced. The “Linsanity” example above is one case – Lin himself was able to trademark the word, but the third party was not. But for incidents like MH 17, the name belongs to no one. It’s a signifier of an event in the mass consciousness, which is where its meaning derives from. This is likely not the last time a trademark will be filed for a phrase or event out of the popular news, but the legal precedent remains.