horse

Horse comes from Old English hors, from Proto-West Germanic *hors/*hross, from Proto-Germanic *hrussą, tracing back to the Proto-Indo-European root *ḱers-, "to run," and *ḱr̥sós, meaning "vehicle."

The word has stayed remarkably stable in form and meaning from Old English hors through Middle English hors/ors to modern English horse, always naming the animal itself.

It's a doublet of car and carrus — both ultimately from the same Proto-Indo-European root meaning "to run" or "vehicle," one path leading to a four-legged runner, the other to wheeled ones.