As in "electronic cash." The same way email is "electronic mail" or efish is "electronic fish."
The concept of eCash is kind of the godfather to the cryptocurrencies of today. It was an evolutionary concept between credit cards and cryptocurrencies.
The concept was put forward by David Chaum in the 1980s that electronic money might be a good idea. The idea percolated for a while before Chaum founded a company called DigiCash to make it a reality. It never really caught on, and DigiCash went bankrupt in 1998.
But, of course, you can't go anywhere today without hitting your head on a Bitcoin. It was just a little ahead of its time.