It seems to be dialectal (MWDEU), or informal (Oxford Online). Anyways, you're in good company: both Dickens and Joseph Conrad used it. And in connection with your other question - it is, of course, an adverb.

Why on earth should you want to condemn a whole word class? This is one of those daft ideas, like avoiding the passive, that some writing schools preach but that good writers completely ignore. The key to good writing is surely judging each word on its own merits, rather than by following these 'writing by numbers' rules.

And why should adverbs be regarded as a "mutation of the English language" - adverbs are hardly unique to English, and even the -ly suffix seems to have developed out of Proto-Germanic (compare with -lich in German), so even the idea of the adverbial suffix is a lot older than English. In fact the word adverb itself comes from Latin (adverbium), a language somewhat older than English. The fact that so many languages, from all parts of the world, have adverbs might tell you something of their functional usefulness.

There's an article in the Chronicle of Higher Education that might answer your question. It's by professor of linguistics and co-author of the Cambridge Grammar of the English Language, Geoffrey Pullum:

http://chronicle.com/blogs/linguafranca/2013/02/20/being-an-adverb/

@Xannatos - you do realise, I hope, that it was The Librarian's joke that was "improper", not his grammar. And as he only wrote one sentence, how can "both sentences" be (I presume you mean grammatically) improper? His sentence did however include two similar "-ing" clauses, neither of which should take a comma:

In the first clause, "your Uncle Jack" is the direct object of "helping" and "off a horse" is a prepositional phrase.

in the second clause, "your uncle" is the direct object of "helping" but also the subject of the phrasal verb "jack off", which has its own direct object, "a horse"

The two parts of a phrasal verb are never separated by a comma, so I can only presume that you are blessed with such a clean mind that you didn't realise that that's what it was, in which case I'd check "jack off" in a good dictionary. The capitalisation of "helping" is neither here nor there, it's the difference between "your Uncle Jack off" and "your uncle jack off" that is crucial.

@alicelee - there's been quite a bit about it in the British press over the last couple of weeks, but it's a bit of a storm in a teacup, I think. The council in question hadn't been using apostrophes on new road names for a few years, without comment, and Birmingham did something similar a few years ago, again without much fuss.

There's already a lot of inconsistency in existing place names; in London some people aren't quite sure whether it's King's Cross or Kings Cross (officially it's with) - see the map here:

http://londonist.com/2011/10/should-kings-cross-have-an-apostrophe.php

And then there's Barons Court tube station, which is just off Baron's Court Road. In Lancashire there's a St Helens, and on the Isle of Wight a St Helen's. There's a town not far from London called St Albans, but in London itself St Alban's Street. The district of St Pauls in Bristol usually goes apostrophe-less, while its namesake cathedral in London is generally blessed with one.

The Plain Language Commission (an unofficial body) in a refreshingly sensible article on the Devon affair note that:

"Our resident grumpy grammarians note that such stories tend to appear in newspapers that forget to apostrophize expressions like two weeks notice (read two weeks’ notice) and three days pay (read three days’ pay), even as they lecture their readers about grammar and falling standards."

They make the point that most of us don't use full stops in abbreviations such as the BBC or NATO any more; and wonder if apostrophes are really any different. The US seems to manage perfectly well without them (apart from five exceptions, apparently).

http://www.clearest.co.uk/news/2013/3/20/Aberrant_apostrophe_anguish_again

Not longitudinally, evidently, but attitudinally [sic] ?

I'll no doubt get jumped on for following 'It sounds like' with a clause, so I just thought I'd get it in first. Not that I really care; according to MWDEU I'm in good company.

@Mommy B - It sounds like your Portuguese friend is barking up the wrong cork tree.

'It is generally agreed these days that the name Jiggs Dinner, referring to the common Newfoundland meal of salt beef (or salt pork spare ribs), boiled vegetables and steamed pudding got its name from the popular comic strip "Bringing Up Father", which began back in the early 1900s. In that comic, the main character was an Irish lad named Jiggs, whose favorite meal was corned beef and cabbage.'

From a food blog by the "Wicked Newfoundlander"

http://awickedscoff.blogspot.com/2009/06/jiggs-dinnernew-england-boiled.html

Hi Skeeter
From what I understand, simply groups of people, for example political parties. In an essay on the semantics of 'mob', one academic suggests that 'Edmund's use of head of mobs suggests the position of authority over a heterogeneous mass of people'. Just google the quote to see various discussions.

Edmund repeats both areas a clergyman should not be:
'(he) must not be high in state' - '(he) must not head mobs'
'or fashion' - 'or set the ton in dress'

In the past they were more or less interchangeable, until the end of the 19th century an editor of the OED thought the distinction would be useful. In Britain, Fowler strongly disagreed with him, and his advice was more or less ignored. But in North America his idea was taken up and some (but by no means all) people now insist on the distinction that Dai Alanye makes.

On one thing we're all agreed - farther is only use for distance, not 'more' or 'in addition to'. But in Britain we have no restrictions ion the use of further to the meaning of 'more'.

In Britain, as Fowler predicted would happen, most people use further for everything, a process that started in the first half of the 19th century:

http://books.google.com/ngrams/graph?content=farther+than%2Cfurther+than&year_start=1800&year_end=2000&corpus=18&smoothing=3&share=

So, as farther is not used very much, it could sound a bit old-fashioned to some younger generations.

A site search of the BBC brings up 19,400 for further, 134 for farther. The ratios further to farther are 307,000 to 11,400 at the Guardian, 257,000 to 2,200 at the Independent and 182,000 to 4590 at the Telegraph.

Most of the stuff on the Internet gives the American angle, with the distinction, so last year I wrote a post giving the British perspective:

http://random-idea-english.blogspot.com/2011/10/q-further-or-farther-british.html

@alicelee - Georgy Porgy appears to be what we call a Little Englander in my neck of the woods.