Even more than "a couple of years". About 15 years ago I worked at a day trading firm and we were writing models that used machine learning. At the time we thought of it more as "computational statistics", but its basically what is called ML now and taught in ML courses (although we didn't use Neural Nets).
BTW, even in 2001 we were far from the first to do this.
Depending on where you draw the line between statistics and machine learning, it could be argued to have originated with Bachelier's thesis in 1900 [1], or Thorp's adaptation of Kelly's work first to gambling and then to finance in the early 60s (he may have been first to use computers for this kind of thing) [2] or maybe with James Simons' Renaissance Technologies in the early 80s [3].
Almost everything I see on neural nets are related to either image processing or text processing. Rarely time series or traditional DB type data -- is there a classic hello-world example or common demonstration of how neural nets are applied onto tabular data common in financial markets?
BTW, even in 2001 we were far from the first to do this.