Today, the verb marshal serves as either a verb meaning "muster troops" or as a noun referring to a specific high-ranking military officer. The former came from the latter, and that traces to an earlier meaning of "court officer". As Old French mareschal, it meant "commander of a household", and as the even earlier Medieval Latin word mariscalcus, the title was given to the commander of a lord's stables. This traces to Old High German marahscalc, which meant "horse servant". The first part of that is basically the Proto-Germanic word for "horse", marhaz (also the etymon of mare; from Proto-Indo-European markos) and the second bit derives from PIE kelh, "to cleave". The given name Marshall is from the noun marshal and usage of the word has steadily been declining over time.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.