Blaise Pascal in the 1600s contributed some of the initial theory to this field. But the term originates from the work of [Daniel Bernoulli]?, it is based on the title of his work called Hydrodynamica (1738). He worked with Leonhard Euler, and they established the general equations of hydrodynamics.
The practice was continued by men as [Joseph Louis Lagrange]? (1736-1813) with the Euler-Lagrange system, [Jean Le Rond d'Alembert]? (1717-1783) discovered the Cauchy-Riemann equations , [Pierre Simon Laplace]? (1749-1827) with the governing equation in the potential flow named after him, [Hermann Ludwig Ferdinand von Helmholtz]? (1821-94) and [William Thomson Kelvin]? (1824-1907) with Kelvin-Helmholtz Instability (see also Rayleigh-Taylor and Richtmyer-Meshkov) as well as Helmholtz's work on vortices.