A lot depends on grasping the image that lies behind the idiom. Replies have explained "on the ropes" (boxing) and "showing the ropes" (introducing a
novice to the ship's working equipment). I would have thought that "up in the air" was a ball-game metaphor, as long as it means "not yet decided".
Military people might talk about their flank being "in the air", but that's a different situation.
I've never understood the American expression "on the line", because I can't imagine what kind of "line" is being assumed in the metaphor. "My job is
on the line"; Fishing line? (Being used as bait) Boundary line? (could go either way). Tight-rope? (could fall either way). Firing-line? (everybody's
shooting at me).
Some idioms are distortions arising out of jokes and misunderstandings, which confuses the issue. I once saw the question "Why do street salesmen say
'Cheap at half the price?' Surely 'twice the price' would be more logical." My answer to that would be that "twice the price" was the original
expression, then somebody thought up the joke variant, and the joke variant became the norm.
When someone makes a mistake, people say "he's put his foot in it". When I was young, as far as I remember, the "it" was understood to be an imaginary
cow-pat. He had made a metaphorical false step. Then somebody came up with the combined image "every time he opens his mouth, he puts his foot in it".
Now, as far as I can tell, this joke version has taken over; "putting his foot in it" is
always assumed to mean "putting his foot in his
mouth", an image which will become an inexplicable puzzle if nobody remembers the original version.
Again, people used to say "If you think that, you've got another 'think' coming". Now sloppy pronunciation and the way the people are so imitative in
their speech appears to have turned "think" into "thing", and it doesn't bother anyone that the remark "You've got another thing coming" has no
discernable meaning.
There is a British idiom "grasping the nettle". I discovered on Google once that half the internet does not understand this term, and wants to
"correct" it to "grasping the metal". So let me explain. There is an English country weed called a "stinging nettle", because it stings. If you
accidentally brush the back of your hand against one, you soon find out (fortunately another plant provides a natural antidote). Now folklore says
that the plant will not sting if you grasp the stem
firmly, This has a metaphorical use. Some kinds of problem can be so tricky that dealing
with them in a tentative way only makes things worse. You need to tackle the problem
firmly and decisively; "Grasp the nettle".
On the subject of British idioms; "waiting for the penny to drop".If someone is visibly failing to understand or grasp the significance of what he's
just been told, the other person might say "I'm waiting for the penny to drop", or perhaps "the penny's dropped" when he sees a change of
expression.
This goes back to the old-fashioned dispensing-machines, of chocolate or cigarettes, as used to be found on railway stations. The internal working of
these machines was obviously mechanical. When a customer inserted a coin of the right shape and weight, the fall of the coin would trip a lever; the
lever would open an internal door, which would allow one bar of chocolate to drop into a dispensing drawer. The customer would then open the drawer
and take the goods. But if the customer was impatient and pulled out the drawer too quickly, the chocolate would be caught half-way through the drop
or fall behind the open drawer, the drawer would jam, and neither he nor anybody else for the next six months would be able to get anything out of the
machine.
So there would be a prominent notice on the machine- "WAIT FOR THE PENNY TO DROP". I've seen them. To be exact, the price had gone up by the time I
was wandering the country on interviews, so the notice now said "WAIT FOR THE COIN TO DROP". But the principle was the same. That mechanical process,
with the enforced wait, became a metaphor for those occasions when a person's mind is visibly taking some time to work things out.
edit on 26-8-2020 by DISRAELI because: (no reason given)