The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A kind of stroboscope consisting of a large wheel with spokes, which when turned at speed is illuminated by momentary flashes of light passing through slits in a rotating disk. By adjusting the succession of flashes, the wheel can be made to appear to be motionless, or to rotate more or less slowly in either direction. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.