Did Barack Obama wiretap Donald Trump’s office, or merely “wiretap” them? On 4 March, Trump tweeted: “Just found out that Obama had my ‘wires tapped’ in Trump Tower.” At a press briefing on Monday, those quotation marks formed the basis of a justification for the outlandish accusation. “The president used the word ‘wiretap’ in quotes,” said Trump’s press secretary, Sean Spicer, using his fingers to make the air-quote sign, “to mean broadly surveillance and other activities.” The quotation marks, he said when pressed, meant the president was “referring to surveillance overall”. So, not necessarily wiretapping then – handy should evidence fail to materialise in future. Or “evidence”, as Trump might say.

It’s a distancing tactic, says Philip Seargeant, senior lecturer in applied linguistics at the Open University. “It’s part of a strategy Trump has of saying things he can deny later, and this is a perfect example. He also does this generally, saying something without committing to it by using ‘You tell me’ or ‘I guess’.”

When used this way, quotation marks are also known as scare quotes. They are are working hard at the moment; when they’re not being used by the president hedging his bets against being found out in future, they are being used to signify a writer’s irony or snarkiness. They allow you to say things you’re really not sure about or refuse to convey legitimacy to (for instance, this paper refers to the “alt-right”). And they’re a very modern phenomenon. The Atlantic last year described the scare quote as “2016 in a punctuation mark”, tracing its evolution from its first recorded use in 1956, in a paper by the Cambridge philosophy professor Elizabeth Anscombe, to the way we infuse terms such as “post-truth” and “politically correct” with judgment.

“If you put something in quotation marks, you’re distancing yourself from it: ‘I’m not saying it’,” says Ruth Finnegan, anthropologist and author of Why Do We Quote?, a history of the quotation mark. “But quotation marks are both far and near. If you say something in quotation marks, you’re associating yourself with it – you may be criticising it, but you’re still making it your own.” Quotation marks go back to the ancient Greeks, she says. “They used to put it in the margin of things and it meant ‘There’s something funny here,’ or ‘Look at this.’” Later, and for a long time, “it was only the Bible or the church fathers who were thought of as [worthy of being] quoted. Then it came to be government or kings, then famous people, and it wasn’t until the 19th century when you had dialogue in novels that it came to be ordinary people [who were quoted].” Now quotation marks have also come to denote sarcasm, or an arm’s length deployment of words.

The scare quote’s parallel in speech is the air quote, which really took off in the 80s. The comedian Steve Martin has been credited with popularising it (although there is a reference to the gesture in a magazine from the 20s). In the 90s, it wasn’t possible to have a conversation without at least one party doing the bunny-ears sign with their fingers, before everyone agreed it marked you out as insufferable. On the campaign trail, Trump liked to use it, particularly when referring to Obama as the “quote ‘president’”. So we can “thank” the president for doing his best to revive it.