vortex (n.) 1650s, "whirlpool, eddying mass," from Latin vortex, variant of vertex "an eddy of water, wind, or flame; whirlpool; whirlwind," from stem of vertere "to turn" (from PIE root *wer- (2) "to turn, bend"). Plural form is vortices. Became prominent in 17c. theories of astrophysics (by Descartes, etc.).

Vortex structures are defined by their vorticity, the local rotation rate of fluid particles. They can be formed via the phenomenon known as boundary layer separation which can occur when a fluid moves over a surface and experiences a rapid acceleration from the fluid velocity to zero due to the no-slip condition.