Chiefly used with the definite article the, the colloquial Australian-English phrase back o’ Bourke denotes a remote and sparsely populated inland area of Australia.

This phrase occurs, for example, in Smitten by a Merc ragtop, published in The Age (Melbourne, Victoria, Australia) of Thursday 24^th August 2000—in the following, Michael Salisbury, aged 61, talks about his motorcar, a 1964 Mercedes-Benz 230 SL coupé, which he has owned for 22 years:

I don’t drive fast, really, because I only drive around the city. I’m always dubious because of the car’s age. I have this fear that I’m going to be let down somewhere in the back o’ Bourke, so I just don’t take long trips in it.

The phrase back o’ Bourke refers to Bourke, the name of the most remote town in north-western New South Wales. The following explanations are from The Australian Language (Sydney and London: Angus and Robertson Ltd., 1945), by Sidney John Baker (1912-1976):

Outback Australian place-names are featured in numerous idiomatic phrases. For instance, back o’ Bourke signifies a great distance inland, go to Bourke! means go to the devil! and from here to Bourke is a metaphorical measure of great distance.

—Cf. also the phrase there’s no work in Bourke, which sometimes follows the phrase things are crook in Tallarook, used of any adverse situation.

The phrase back o’ Bourke is first recorded in the following poem by the Scottish-born Australian poet and journalist William Henry Ogilvie (1869-1963), published under the pen-name of Glenrowan in The Bulletin (Sydney, New South Wales, Australia) of Saturday 15^th February 1896—whether William Henry Ogilvie coined the phrase back o’ Bourke or popularised it is not known:

Bards of the Backblocks.
[For The Bulletin.]
AT THE BACK O’ BOURKE.

Where the mulga paddocks are wild and wide,
That’s where the pick of the stockmen ride,
At the Back o’ Bourke,
Under the dust-clouds dense and brown,
Moving Southward by tank and town,
That’s where the Queensland mobs come down,
Out at the Back o’ Bourke.

Over the Border to and fro,
That’s where the footsore swagmen go,
At the Back o’ Bourke;
Sick and tired of the endless strife,
Nursing the bones of a wasted life
Where all the sorrows of Earth are rife,
Out at the Back o’ Bourke.

Whether the plains are deep or dry,
That’s where the struggling teams go by
At the Back o’ Bourke,
North and Southward, in twos and threes,
Bullocks and horses down to the knees,
Waggons dipped to the axle-trees,
Out at the Back o’ Bourke.

That’s the land of the lying light
And the cruel mirage dancing bright—
At the Back o’ Bourke;
That’s where the shambling camel train
Crosses the Western ridge and plain,
Loading the Paroo clips again,
Out at the Back o’ Bourke.

That’s the land of the wildest nights,
The longest sprees and the fiercest fights,
At the Back o’ Bourke;
That’s where the skies are brightest blue,
That’s where the heaviest work’s to do,
That’s where the fires of Hell burn through,
Out at the Back o’ Bourke.

That’s where the widest floods have birth
Out of the nakedest ends of Earth,
At the Back o’ Bourke,
Where poor men lend and the rich ones borrow;
It’s the bitterest land of sweat and sorrow,
But if I were free I’d be off to-morrow
Out at the Back o’ Bourke.

Glenrowan.

In the above-mentioned book, The Australian Language, Sidney John Baker contextualised both the phrase back o’ Bourke and the publication of Ogilvie’s poem in the Bards of the Backblocks section of The Bulletin:

THE BACKBLOCKS.

Virile though it may sound, the expression Great Outback leaves too much to be taken for granted. We have many synonyms to give us richer pictures of our vast inland country. At the end of last century when the “Bulletin” was at the peak of its influence, the violently pro-Australian writers who filled its pages with bush and outback lore strove to outdo each other in the propagation of terms for the inland.
Here are some of their best offerings: back-of-beyond, (also back-o’-beyond), outback, wayback, rightback, back-o’-Bourke (New South Wales), back-o’-outback, beyond outback, behind outback, set-o’-sun, death-o’-day, past-west, westest-west, beyond set-o’-sun, right behind death-o’-day, right at the rear of back-of-outback.
These were, in the main, variations on the theme of backblocks. The use of block for an area of land was applied originally in the 1850s to areas which the Government had split up for settlement. Today, we have blocks varying in size from a few acres to 10,000 square miles, but they are still known as blocks.
A backblock was originally more or less what it purported to be—a block or section of land in a remote part of a sheep or cattle station. But as these backblocks were populated the term came to denote inland country in general.

The phrase back o’ Bourke then occurred, with explicit reference to ‘Glenrowan’, in Answers to Correspondents, published in The Bulletin (Sydney, New South Wales, Australia) of Saturday 4^th April 1896:

Ribleur: What you want “Glenrowan” to tell you:—
“Did ever yer have yer pack-horse die
Out on the hell-fire plains that lie
At the back o’ Bourke;
Miles to travel to water or toke,
Boots all busted, pocket broke,
Not even a whaler to lend yer a smoke,
Out at the back o’ Bourke?”

In the following from The Bulletin (Sydney, New South Wales, Australia) of Saturday 18^th July 1896, back o’ Bourke was already used as a well-established phrase:

What has become of the N.S.W. anti-camel agitation? Has the Westralian demand for the Bourke teamsters’ bête noir disposed of the trouble? Or has the agitation died a natural death? What a dust that camel-question did raise! Apropos of the way the great camel controversy spread when it got fairly started “out at the back o’ Bourke,” a Maorilander writes:—“When the agitation was going strong against the camels and their drivers I happened to be a passenger by express-tram from Sydney to Melbourne. [&c.]”