The story
From how attempting to slow below this speed by pulling back on the nose will cause the aircraft to stall.
Etymology from Wiktionary, CC BY-SA 4.0.
stall speed
Today it means: The airspeed at which the lift generated by an aircraft flying with an angle of attack equal to the stall angle (the point of maximum lift for a given airspeed) is exactly equal to the aircraft's weight; the minimum airspeed at which it is possible to maintain level unaccelerated flight. Full definition →