Anyone exceeding the boundaries of convention or taking risks is said to be “pushing the envelope.” The phrase is so widely circulated that we don’t exactly question it, though it superficially doesn’t seem to make a lot of sense. Why would ambition be related to moving an envelope around? Why do we invoke stationery?

Actually, we don’t. In this context, envelope doesn’t mean postal or paper correspondence. It’s instead referring to the aeronautical term of the limitations of a physical space or technology.

According to Merriam-Webster, both the noun envelope and the verb envelop come from the Anglo-French word envoluper, with voluper meaning “to wrap.” In the context of air travel, the envelope refers to the operating threshold of aircraft. To push a plane past its speed limits, or past the limits of altitude, would be to exceed—or push—its envelope.

The phrase apparently entered the mainstream lexicon thanks to Tom Wolfe. The author’s 1979 book The Right Stuff, which detailed the early days of American space exploration, referenced pilot Chuck Yeager going through “the supersonic envelope.” Pilots, Wolfe wrote, were often talking about “pushing the outside of the envelope.” He believed the metaphor may have originated with test pilots at the Patuxent River Naval Air Station in Maryland in the 1940s, based on the “envelope” of air or gas containers in balloons and airships.

Wolfe added the metaphor was spoken of in terms of flight testing:

“The 'envelope' was a flight-test term referring to the limits of a particular aircraft's performance, how tight a turn it could make at such-and-such a speed, and so on. 'Pushing the outside,' probing the outer limits, of the envelope seemed to be the great challenge and satisfaction of flight test.”

In most examples, the envelope is an enclosure to be breached and is often associated with innovation. Or, if pushing the envelope is dangerous, with risk. It's all about pushing boundaries, and has nothing to do with remaining stationary.

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