Well, the Oxford dictionary says that it means '(information) from an authoritative source'; and I guess that the origins lie in horse racing. In other words it's a tip from someone who is in a position to know.
This particular tip relates not to racing but to another form of gambling, namely publishing. Yesterday a real live actual British agent made a comment on an earlier post of mine which I think deserves to be dragged out into the full light of day, because info from agents is usually worth passing on.
This particular piece of info/tip relates to writing novels -- a distressingly bad habit, like biting your nails, which some of you seem to have picked from mixing with entirely the wrong people.
This is what the (anonymous) agent has to say, in response to my post about Francis Ellen's novel The Samplist:
It's interesting how often struggling writers embittered by rejections from countless agents and editors hurl their derision on the idea of a Big Brother contestant having his or her autobiography published as an example of taste subordinated to commercial viability. As far as I know, no Big Brother contestant has ever had their autobiography published by a trade publisher, and no agent or editor worth his or her salt would even think of commissioning such a book.
As an agent, the first thing I look for in a fiction submission is precision; the precise elucidation of ideas. It's a prerequisite for reading beyond the first page or two (though it's not enough on its own; it has to be accompanied by narrative flair). I'm not surprised Paul [another commenter on the same post] hasn't found a publisher, if his scattergun rant is any evidence.
Incidentally, I don't give a damn whether a novelist attended a particular school, or who they know. I'm only interested in the quality of the writing, and I speak for a very large majority of my fellow agents in saying so.
That said, in the case of certain high-profile novelists, I do think a deeply conservative and depressing prize-giving / reviewing culture has developed. Positive reviews and reputations do indeed gather their own momentum regardless of the quality of the author's most recent novel, and today's Booker longlist is evidence of the fact. Ian McEwan, Rushdie, and Zadie Smith - presumably the favourites to win - are trading on reputation alone; all three new offerings are embarrassingly bad.