The word 'speed' has undergone a fascinating journey of semantic narrowing. Its earliest meaning in Old English was centered on the concept of "success" or "prosperity," a sense still faintly echoed in the archaic expression "God speed you." The logic connecting prosperity to velocity lies in the idea of favorable progress or advancement. From denoting a successful outcome, the meaning gradually shifted to emphasize the rate of that successful progress, eventually specializing to refer specifically to quickness or velocity. Thus, the modern abstract meaning of "rate of motion" evolved from a more concrete ancestral idea of thriving and favorable advancement.

The word is a simplex form. It originates from the Old English 'spēd', meaning "success, prosperity, quickness, velocity." This Old English term is derived from the Proto-Germanic 'spōdiz' (success), which in turn comes from the Proto-Indo-European root 'spē-', meaning "to thrive, prosper."