celerity (n.)

"swiftness, rapidity of motion," late 15c., from Old French celeritee (14c., Modern French célérité), from Latin celeritatem (nominative celeritas) "swiftness," from celer "swift," from PIE *keli- "speeding" (source also of Sanskrit carati "goes," Greek keles "fast horse or ship," Lithuanian šuoliai "a gallop," Old High German scelo "stallion").