In Australian English, the plural noun apples is used as a predicative adjective in phrases such as everything’s apples and she’s apples, which mean everything is all right.

(The pronoun she is used colloquially in Australian English to refer to a thing to which female gender is not conventionally attributed, especially a condition or a circumstance.)

The origin of this use of the plural noun apples is unknown.

In A Dictionary of Australian Colloquialisms (Sydney University Press in association with Oxford University Press Australia, 1990), Gerald Alfred Wilkes (1927-2020), who defined everything’s apples as meaning in good order, under control, proposed two hypotheses:
– that apples is from apple-pie order, which denotes perfect order or neatness;
– that apples is short for apples and spice, rhyming slang for nice.

Several dictionaries—for example The Oxford Dictionary of Modern Slang (Oxford University Press, 2008), by John Ayto and John Simpson—assert that apples is short for either apples and spice or apples and rice, rhyming slang for nice.

However, no documentary evidence seems to support this assertion, and I personally find more convincing the hypothesis that apples is from apple-pie order.

The Australian-English use of apples in phrases such as everything’s apples and she’s apples may have originated in the slang of the Australian armed forces during the Second World War, because all the earliest occurrences of apples that I have found are from texts dating from 1941, 1942 and 1943, and because all of those texts (with one exception) refer to Australian servicemen.

These are, in chronological order, the earliest occurrences of apples that I have found:

1-: From the column Jack Davey’s Day, published in the Daily Telegraph and Daily News (Sydney, New South Wales) of Friday 14^th February 1941:
—This is the only text set in a civilian context. This text contains several rhyming-slang expressions; for example: skin-and-blister, rhyming slang for sister, and smuggle-and-smother, rhyming slang for brother. Since none of those rhyming-slang expressions is truncated, it is doubtful that apples in “everything was apples” is short for either apples and spice or apples and rice, rhyming slang for nice:

Everything Jake
“Now everything was apples. He could not only buy his skin-and-blister a poet-and-peasant, but he could get a tit-for-tat for his old woman, a pair of Cockatoo-Docks for his smuggle-and-smother, a small Aristotle of half-in for his old pot-and-pan, and also he’d have a couple of Dean-Dillons left over to take his Mother-o’-Pearl to the scratch-and-itches.”

2-: From West Australian Casualties, published in the Daily News (Perth, Western Australia) of Thursday 26^th June 1941:

Private Sydney Cant went to Greece.
After the Greek evacuation he cabled: “Everything apples.”
Since then his parents have been notified of his being missing.

3-: From the column Diggers’ Diary, published in The Western Mail (Perth, Western Australia) of Thursday 18^th December 1941:

“She’s Apples”

Being an account of an experience in North Africa recounted by Sergeant M. L. Brabazon, formerly of Clyde-st., Mt. Lawley.
Last Easter an attack by “Jerry” on our perimeter defences was expected, and hasty arrangements were made to strengthen the post we occupied by pushing in any available “Iti” weapons.
“Apples,” the battalion postal orderly, with two members of the Battalion H.Q. office staff, were occupying an open sangar near Battalion H.Q., and this was selected by the C.O. as an ideal spot to place an “Iti” 47 mm. anti-tank gun.
Events moved fast, and when a corporal brought along the gun to run it into position the occupants raised a howl about having to shift from the position they had prepared for themselves, as living and fighting quarters.
Further consternation was caused when, on inquiry from the corporal as to what men were to man the gun, the reply came: “You are.”
“Apples” immediately saw red and ejaculated: “I’m going to get an understanding on this—either I’m a postal orderly or an anti-tank gunner; I’m not both.”
The corporal, continuing with the placing of the gun, reassured him and offered them advice as to the handling, loading and firing of the weapon, also how to squint down the barrel for a rough aim.
The postal orderly’s final response was: “She’s Apples.”
Darkness was approaching, so the three anti-tank gunners, reconciled to their unhappy position, placed the ammunition in a handy place ready for use. Throughout the night they “stood to” in turns, keeping a constant vigil, and were greatly relieved when dawn broke.
They had done their job and were pleased the threatened attack on our post had not eventuated but had taken place in another sector.
The corporal came along and during a “once over” found that in the hurry of the previous night the ammunition had not been primed! Imagine the feelings of the three anti-tank gunners!
After the first dread thoughts had passed away out came the postal orderly’s final remarks: “Wouldn’t it ——. Anyhow, she’s apples.”

4-: From Taffy was an Orchid, a short story by Aura Z. Jackson, published in The Australian Women’s Weekly (Sydney: New South Wales) of Saturday 12^th September 1942—Taffy is an air-force officer:

I phoned him.
“Hullo, Taffy, Jane calling. How are you?”
“She’s apples,” said Taffy.

5-: From Target Area (Sydney, New South Wales: Australasian Publishing Co. Pty. Ltd., 1943), by John Binning—this book tells the story of the author and his comrades, soldiers at an advanced operational base at Darwin, in the Northern Territory, during the Second World War:

The Americans say “gee whiz” like natives. They have also an affection for “bastard” in its friendly, Australian sense. If everything is running smoothly “she’s apples.” That phrase goes for all of us. We speak and understand the same idiom.