The Collaborative International Dictionary
Brownian movement
Brownian \Brown"i*an\, a. Pertaining to Dr. Robert Brown, who first demonstrated (about 1827) the commonness of the motion described below.
Brownian motion, Brownian movement, the peculiar, rapid, vibratory movement exhibited by the microscopic particles of substances when suspended in water or other fluids.
Douglas Harper's Etymology Dictionary
Brownian movement
1871, for Scottish scientist Dr. Robert Brown (1773-1858), who first described it.