1913, "give a streamline form to," from streamline, n.. From 1936 in the extended sense of "simplify and organize." Related: Streamlined; streamlining.

1868, "line drawn from point to point, so that its direction is everywhere that of the motion of the fluid" [Lamb, "Hydrodynamics," 1906], from stream, n. + line, n.. The adjective is attested from 1898, "free from turbulence," 1907 in sense of "shaped so that the flow around it is smooth."