Definition: to be mentally unstable/crazy
Martin proudly presented the sandwich he had made to his family. “It’s peanut butter and turkey,” he announced.
“Are you off your rocker?!” was the response.
First of all, this idiom doesn’t discriminate. It doesn’t have to be ‘your’ rocker. It can be his, her, or theirs.
But what is this rocker it refers to? The image and explanation that most commonly comes to mind is somebody, especially an elderly person, physically falling off their rocking chair. This doesn’t seem to have any bearing on the idiom as this points to a physical issue, not a mental one.
The origin is most likely a mechanical one.
Within many machines, a rocker is a sort of regulator which helps control its performance. If this rocker slips or becomes misaligned, the machine will work incorrectly, if at all.
There is a similar phrase with the same meaning which appeared in the English language at the same time, to be ‘Off your trolley‘. This seems to refer to the overhead lines that provide power to trolley cars. If the car loses contact with this line, there is a loss of power and the trolley grinds to a halt. There are some claims that the wheel that made this connection was sometimes referred to as a rocker, but whether it was or not, it is clear that the two idioms are likely from the same source.
Iddy’s never hopped on or off a trolley car. It’s probably a good thing as he has a hard enough time just sitting in a chair.
Definition: something extremely expensive
Example: Randolph wanted an indoor swimming pool. As much as Julie wanted one herself, she had to be the reasonable one. “Are you kidding? That would cost an arm and a leg!”
Okay. Let’s get the most commonly believed origin story out of the way, because there’s no truth to it.
Portrait painters, over the past centuries, had a fixed price for a standard head and shoulders portrait. If you wanted the torso included, the portrait would be more expensive. If you wanted the full body painted, that would be still more. Though it is likely true that a full body portrait would cost more than a traditional head and shoulders one, it is unlikely the artists charged by the limb! On top of that, the phrase doesn’t appear to have entered the language until after the Second World War, well after the age of portrait painting.
It is more likely to have come from an earlier nineteenth century phrase, often expressed in terms similar to ‘I’d give my right arm for that’, though there were left varieties of the phrase, as well as other limbs and organs quoted. In other languages, there are phrases that seem to support this. In France, something may ‘Cost the eyes from your head’. In Bulgaria, something may ‘Cost your Mother and Father’.
Another explanation ties in with the idiom’s introduction to the English language after the war. Many soldiers returned home to America (where the phrase appears to have originated) missing limbs. This indeed was a high price to pay for their country. It had cost them an arm and a leg.
I really don’t want to know where Iddy got his extra limbs from.