You've probably heard the name a million times: "Microsoft Windows." But how did the operating system get that way, and why isn't it named after something else---like doors or ceilings? We'll explain.
Microsoft Interface Manager
In 1981, Microsoft began developing the rudiments of what would later become Windows. Originally called Interface Manager, it would add a graphical overlay to MS-DOS, allowing visual program control using a mouse (instead of typing keyboard commands). It would also allow multitasking by showing different applications within boxes placed in different areas of the screen simultaneously---a concept pioneered at Xerox PARC with its Alto and Star computers and later refined at Apple.
In the computer industry at the time, these simultaneous on-screen program boxes were called "windows," and software that managed them were usually called "windowing systems." In the early 1980s, many vendors developed their own windowing systems for PCs, including IBM with TopView, Digital Research with GEM, and VisiCorp with Visi On. Microsoft's "Interface Manager" would be one of many when it finally launched several years later, and Microsoft knew it.
Enter "Windows"
In 1982, Microsoft hired a new marketing VP named Rowland Hanson, who was a veteran of the cosmetics industry. Hanson brought a new angle for defining Microsoft's brand that involved placing the "Microsoft" name in front of its products with a generic or simple word after it, such as Microsoft Word and Microsoft Excel.
While researching a new name for Interface Manager, Hanson reviewed trade articles about this wave of PC multitasking systems and pointed out what they had in common. He noticed the term "window" used a lot in the context of terms like "windowing system" and "windowing manager," so he latched onto "Windows" as a generic term that would help Microsoft own the entire product category. Every time someone referred to windowing systems from then on, they would tangentially be promoting the "Windows" brand.
According to the book Barbarians Led by Bill Gates, Interface Manager's developers were reticent to switch the name to Windows, and the decision to finally do so came down to Bill Gates. Once Gates was behind the name, the developers fell in line---and Microsoft Windows was born.
The Windows Legacy
Microsoft announced Microsoft Windows publicly on November 10, 1983---far before the product was ready to ship---in an attempt to get hardware and software vendors on board with the "operating environment," as Microsoft called it. It had its intended effect, since several competitors were working on PC windowing systems in the early 1980s.
When Windows 1.01 launched in 1985, it wasn't a breakthrough product, but it evolved over time from a MS-DOS shell to a standalone operating system, then into the mammoth brand we all know today. Windows is a multi-billion dollar business, and as long as there's billions of dollars attached to the "Windows" name, Microsoft will probably keep using it for years to come.