From spread + sheet.
(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “When was the term first used?”)
1985 September 15, Erik Snadberg-Diment, “Number Crunching on the Macintosh”, in The New York Times[1], →ISSN:
The program's most quintessentially Macintoshian feature, one as yet unique among spreadsheets, is its icon bar, which resides at the top of the screen just below the standard menu bar.
2009, Fred Vallance-Jones, David McKie, Computer-Assisted Reporting: A Comprehensive Primer, Oxford University Press, →ISBN, page 49:
A little later in this chapter, we'll run through some of the most common methods journalists use to analyze the material they gather and store in spreadsheets.
If you'd spreadsheeted the cascade charts and sorted it by each name's sphere of influence, then the people Carrie Johnstone sent the police to get constituted a big chunk of the middle third—people who “commanded” maybe four of five others—and maybe 10 percent of the top influencers.