What is the "line" in "cash on the line"? Is it a ship mooring line?
In the phrase "cash on the line" (immediate payment, payment during the transaction), what was "line", originally? I suspect it was a ship mooring line but I'd like to be sure. (I imagine a ship coming in with goods that are in demand, and business people show up in port and the ship insists they pay on the spot (by the mooring line) before the ship will unload the goods to give to them.)
I found the following sites with definitions of the term but they lack the origin:
http://idioms.thefreedictionary.com/cash+on+the+line
http://esl-bits.net/idioms/id111.htm
Solution 1:
A Hypothesis
I believe that "line" is here being used to refer to a contract. This is the same line from "sign on the dotted line", which hews closely to the idea that money is exchanged directly after a contract is signed.
Admittedly, there are a lot of ways to say the same thing and the documents are sketchy so I don't think that I can prove this definitively. I don't think that it refers to shipping, however. First, if it did I would expect that the term would be much older than it is (see below). Second, while the shipping idea is nice when you think about the phrase as it relates to a risky investment (shipping is risky), I can't intuitively connect immediate payment to shipping without first appealing to the underlying contract (if that makes sense).
A Brief Overview of What I Found
Consider this Google Ngram of "cash on the line". Usage first spikes in 1934 - one year after the trough of the Great Depression. The global maximum is at 1940 while a second peak occurs at 1943. (Notice that I have specified American English corpus. Try specifying British English corpus and you can see that this is an American phenomenon.)
Initially - based on the sources where I was finding the phrase being used - I did not think that the malapropism hypothesis held up. "Cash on the nail" seems to be a term favored by the financial press while "cash on the line" was used more widely. However, the fact that usage first spiked at a time of acute economic hardship (1934) may provide a "jumping off" point for its wider, altered use. Here I have in mind something like "toxic asset" post-2008. At the same time, use of "cash on the nail" did not spike in 1934 so this idea only goes so far. Moreover, since it does describe a fairly common act (exchange of money) I don't think that it is necessarily a malapropism. Compare "cash on the line" and "cash on the Nail" to, e.g., "cash down" or "cash and carry".
Based on the peaks in usage in the early 1940s, my pet theory was that "line" was also being used to refer to the front line in a war. Closer reading doesn't bear this out. If anything, "cash on the line" was being used as a synonym for the Cash and Carry program. An example is from this December, 1940 issue of Life:
...what Franklin Roosevelt proposed was that the U.S. stop being just a friendly merchant selling Britain arms for cash on the line and become its non-fighting ally. (See 1)
Billboard seems to have used the phrase quite a bit when describing small time industry deals. For example,
There's quite a few sustaining programs that now offer dough and a few commercials that pay cash on the line. Vick Chemical Company's _Dr. I.Q., which pays off to the tune of $200 for quiz suggestions and $250 for biographical sketches... (See 2)
The idea in most cases seems to be some version of, "You sign, we pay." A final set of examples can be found in the advertisements for the The Curtiss-Wright Technological Institute found in Flying Magazine up to 1942, which invariably mention the cash that students put on the line (tuition).
(I was limited to two URLs.)
books.google.com/books?id=NkoEAAAAMBAJ&pg=PA9&dq=%22cash+on+the+line%22&hl=en&sa=X&ved=0CDEQ6AEwAGoVChMImt74uISRxwIVzJqACh09BAF3#v=onepage&q=%22cash%20on%20the%20line%22&f=false
https://books.google.com/books?id=owwEAAAAMBAJ&pg=PT9&dq=%22cash+on+the+line%22&hl=en&sa=X&ved=0CFIQ6AEwCGoVChMI6buN9vOQxwIVQaCACh2kUQa8#v=onepage&q=%22cash%20on%20the%20line%22&f=false