Nick Clegg says people who pay incredibly low rates of tax are "literally in a different galaxy", highlighting what is arguably one of the most commonly misused words in the English language. But why is the word so troublesome?

According to the Oxford English Dictionary, in its strictest sense, literally means in a literal, exact, or actual sense.

Yet nowadays the idea of an album "literally flying off the shelves" and recipes "literally taking no time at all" barely raises an eyebrow in some quarters.

So is using literally in this manner wrong - or can one word be used in contradictory ways?

English language specialist Prof Clive Upton, from the University of Leeds, says the most "strait-laced" take on the word is its original sense, which is first recorded in 1429 in the Oxford English Dictionary.

But he says the colloquial use of word - which is used to indicate that some metaphorical or hyperbolical expression is to be taken in the strongest admissible sense - is well established.

"If you look at the Oxford English Dictionary, literally was first used in this sense in 1769. There are lots of examples since then, for instance Mark Twain used it in the Adventures Tom Sawyer in 1876 when he wrote 'Tom was literally rolling in wealth'.

"If someone says something is literally the case, they usually want to add emphasis," he says.

Famous literally quotes "...literally will split the child in half to live one week with the mother..." - Ulrika Jonsson of the Swedish system of child custody after divorce

"We're tearing up this place tonight Literally! We're gonna set this sleepy town alight Literally! We'll kill and steal and burn and drink Cause us vikings don't care what you think - The Viking Song lyrics, Horrible Histories

"My legs literally turned to jelly" - Rachel Stevens on Strictly Come Dancing

I have to be involved literally down to splitting the atoms" - Sarah Jessica Parker on her new clothing line

(This album is) "literally flying off the shelves" - Radio 1 DJ Fearne Cotton Source: "Literally tsar" Paul Parry Read more at Parryphernalia

Ian Brookes, consultant editor at Collins English Dictionary, agrees the figurative and metaphorical use of the word crept into the English language as an intensifier.

"The word literal comes from the Latin word littera, which means letter, so when you literally go back to the origin of the word it means letter by letter, in its exact accurate sense, and literally means according to the letter of the language.

"But from the early 19th century it gained another meaning - to give emphasis - for example instead of literally hundreds of people meaning hundreds of people, it could have referred to 80 or 90," he says.

Mark Forsyth, author of The Etymologicon,argues that it is human nature to change words over time. He cites the example of the word "immediately" which originally meant "soon".

Humans are also prone to exaggerate, he says.

"It amuses me that Americans use awesome all the time. They say a bus turning up is awesome, but it can't possibly fill them with awe. I use excellent all the time, without meaning it's excelling. Wonderful doesn't really fill people with wonder, fantastic is strictly speaking like a fantasy."

But he says the slightly unusual thing about literally is its meaning has not evolved slowly, with a slight shift, but the precise meaning has been reversed.

"It's a bit like quite, which used to be absolutely or completely. People still say 'I'm quite happy to do that it' - which means I'm absolutely quite content - but you can also say 'I'm not quite happy' - exactly the same word changes its meaning according to change in tone of voice," he says.

So if literally has different meanings, does its use end up causing confusion?

According to Brookes, the latter use of literally - which is especially common in an informal context - sometimes does not add anything to the meaning of a sentence.

"Someone might say the house was literally only five minutes walk away. They are not saying five minutes in its original meaning, but they are saying quite a short distance."

But he says using literally as an intensifier can often result in "absurdity" in phrases such as "the news was literally an eye-opener to me".

The English language has also become richer in metaphor over time, so when literally is used alongside a metaphor, there can be a humorous contradiction, he adds.

"For example if someone says Swedish people are literally born on skis, they are using figurative language in born on skis, but using literally is conjuring up an image of midwives delivering babies on skis - we laugh because it's a juxtaposition," he says.

So that people avoid becoming the butt of jokes, Collins English Dictionary advises against using literally as an intensifier in formal or written contexts.

"Literally is one of those language bugbears, so we print a special note in the dictionary to advise on the problem," says Brookes.

"There are always two opposing views - those that believe we must use words very carefully, so that language does not lack precision, and the other side which argues that if people try to fossilise language they limit it.

"The problem really only occurs when it is not clear which sense is being used," he says.