An Etymological Dictionary of Astronomy and Astrophysics

The time rate of change of position in a given direction, measured as length per unit time. → speed.

Etymology (EN): L. velocitatem (nominative velocitas) “swiftness, speed,” from velox (genitive velocis) “swift.”

Etymology (PE): Tondâ, from tond “swift, rapid, brisk; fierce, severe” (Mid.Pers. tund “sharp, violent;” Sogdian tund “violent;” cf. Skt. tod- “to thrust, give a push,” tudáti “he thrusts;” L. tundere “to thrust, to hit” (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere “to thrust or bore through;”
PIE base *(s)teud- “to thrust, to beat”) + noun suffix -â.