I know "swings and roundabouts" means "gains and losses that offset each other", but I can't understand. Any story behind this?
When children play at the park, their time on the swings for unexpected reasons may be curtailed so they are allowed extra time on the roundabouts. So what they lost on the swings they gained on the roundabouts.
The metaphor is in wide use in Britain for almost any instance where one needs to point out some compensatory effect that has taken place.
The breakfast was poor in the hotel but there was a sumptuous supper. So what we lost on the swings...
It is all explained by the Free Dictionary
The full expression is
What you lose on the swings, you make up for on the roundabouts.
Its origin is from the fairground. For whatever reason, the fairground owner may be losing money on the swings, but gaining it on the roundabouts. So the situation is balanced.
"They're giving everyone a pay rise, but now we're all expected to work longer hours. So, swings and roundabouts, really..."
It's closely related to the other expression
Six of one and half a dozen of the other
which also means that two things are roughly equal when all the pros and cons are totted up. However, this one is more likely to be used when you're weighing up the situation, before a decision is made:
"If I get the first train, I'll arrive too early and have to wait, but if I get the next train, it will be really full with all the commuters. It's six of one and half a dozen of the other."
I have just read the poem "Roundabouts and Swings" written by Patrick R. Chalmers and published in 1912, which user 160355 mentions.
The third and fourth lines in the second stanza, where the 'Pharaoh' (gypsy/gipsy) answers the question
"'ow d'you find things go?"
"I find […] things very much as 'ow I've always found, / For mostly they goes up and down or else goes round and round."
confirm what I intuited (before having a look at the website below):
on the swings or see-saws, what the person at one end of the plank or beam gains (height, here), the other loses in equal amount, whereas on roundabouts or merry-go-rounds everybody remains on the same level.
A bit subtler than gaining on one machine what you lost on the other!
You get by anyway, with ups and downs at times, and with nothing changing much at other times.
The third and last stanza ends with the line
An' losses on the roundabouts means profits on the swings!
The same machines are used again, in a less graphic manner, no longer to do with the way they move: the idea is of a bad investment (roundabouts, expensive machines to buy and work?) and a good investment (swings, inexpensive 'machines', worked by the users themselves?), one making up for the other… a mind doing the splits between poetry and banking?! (the poet, Irish, was a banker in London, after all…)
The expression comes from the poem "Roundabouts and Swings" by Patrick R Chalmers. The poet was an Irish banker who worked in London around 1900. It's about an encounter with a gypsy (Pharoe) traveling show. It's a great poem!
It was early last September nigh to Framlin'am-on-Sea,
An' 'twas Fair-day come to-morrow, an' the time was after tea,
An' I met a painted caravan adown a dusty lane,
A Pharaoh with his waggons comin' jolt an' creak an' strain;
A cheery cove an' sunburnt, bold o' eye and wrinkled up,
An' beside him on the splashboard sat a brindled tarrier pup,
An' a lurcher wise as Solomon an' lean as fiddle-strings
Was joggin' in the dust along 'is roundabouts and swings.
"Goo'-day," said 'e; "Goo'-day," said I; "an' 'ow d'you find things go,
An' what's the chance o' millions when you runs a travellin' show?"
"I find," said 'e, "things very much as 'ow I've always found,
For mostly they goes up and down or else goes round and round."
Said 'e, "The job's the very spit o' what it always were,
It's bread and bacon mostly when the dog don't catch a 'are;
But lookin' at it broad, an' while it ain't no merchant king's,
What's lost upon the roundabouts we pulls up on the swings!"
"Goo' luck," said 'e; "Goo' luck," said I; "you've put it past a doubt;
An' keep that lurcher on the road, the gamekeepers is out."
'E thumped upon the footboard an' 'e lumbered on again
To meet a gold-dust sunset down the owl-light in the lane;
An' the moon she climbed the 'azels, while a night-jar seemed to spin
That Pharaoh's wisdom o'er again, 'is sooth of lose-and-win;
For "up an' down an' round," said 'e, "goes all appointed things,
An' losses on the roundabouts means profits on the swings!"