A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
The English verb "to excel" means "to be very good at something, to surpass others".
In the early 1980's, Lotus 1-2-3 became the leading spreadsheet program. Microsoft's spreadsheet program Multiplan lagged behind it in popularity. So they set up a team to develop a new spreadsheet that could do everything that Lotus 1-2-3 did, but better. "Excel" refers to that.