When did the usage of "N" to indicate some unspecified quantity come up? I have heard a number of Cantonese speakers use N (pronounced like the English letter) to designate some sort of unspecified quantity, for instance:


  我 N 年前去过。(Approximately "I went there some years ago.")


When did such a usage first come up? Does it have anything to do with the standard mathematical usage of n, and does it also appear in other languages?
As you suspected, it is thought to come from the mathematical usage:

为什么“N”可以代表“很多”的意思?例如N多次,N多个
Why can &quot;N&quot; have the meaning &quot;a lot&quot;? For instance, N-times, N-of-them
因为数学上的数列一般都用第N项代表任一项,可知无穷大的一项.
Because in math, sequences usually use &quot;the nth term&quot; to represent any term, including unboundedly large ones.

Another (perhaps more reputable) source

...n在代数中表示很多，如从1开始到2,到3,..., 到n。因此在口语中n经常用来表示特别多，例如“买了n多电话卡”...
...in algebra, &quot;N&quot; signifies &quot;a lot&quot;, as in &quot;from 1, 2, 3, up to N&quot;. Because of this, in colloquial speech, &quot;N&quot; often is used to express &quot;very many&quot;, as in &quot;to buy sooo many telephone cards&quot;...