A "short" is traditionally someone with expertise in shorting a stock, i.e., managing to borrow shares and sell them in anticipation of a decline in value. Obviously, if there are many people shorting a particular stock at any given time, and if they are wrong about the future, then a steep rise in value if the share price will not only cause them to lose money, it will force panic purchases of stock as the traders attempt to cover their shorts. If the instigator of the squeeze is successful, he will have a corner, and drive the price of the stock up to absurd levels.
An unsuccessful squeeze of shorts in a copper trust triggered the Crisis of 1907. That, in turn, triggered the Aldrich–Vreeland Act (May 1908).
Henry Clews, Victor Niederhoffer, *Fifty Years in Wall Street*, p.149