There was a question the other day that got deleted, and sadly the user deleted their account too, but they were wondering about the similarity between the Roman name "Martial" and the modern surname "Marshall". The question was deleted because it was asking about basic facts, but I thought it was interesting to look at the actual origins of both words.

Martial is the English name of a Roman poet whose full name in Latin was Marcus Valerius Martialis. His cognomen “Martialis” came from the fact that he was born in Martius - the month of March, named after Mars. the Roman god of war. The same word “martialis” could also mean warlike or anything to do with fighting or the military, which is where we get the modern English word martial, as in "martial arts" or "martial prowess". English either borrowed it directly from Latin, or it was borrowed more indirectly in the Middle English period, from medieval French, where it had developed from the original Latin word.

The military rank (and now surname) marshal/marshall comes from the Germanic language family, not Latin. German and Latin are related, in the sense that they’re both part of the Indo-European family, but they’re pretty distant relations. The ancient Germanic words “marhaz” (horse, the same origin as the English word “mare”) and “skalkaz” (servant) were actually borrowed into Latin in the Middle Ages, as “marescalcus”, and then evolved into marechal in French and was borrowed into English as marshal. Originally, a medieval marshal was the person in an army who was responsible for taking care of the horses. The -shal part is also found in the name of another medieval military commander, the seneschal. (By the way, “constable” also comes from another medieval horse-related position, the “comes stabuli” or the commander of the stables.)

“The office of marshal was an ancient one. The Latin word marescallus or marescalcus preserved two ancient Frankish elements meaning ‘horse-slave’; it seems very likely that the word was being applied to the unfree grooms of the ancestors of the Merovingian kings of the Franks. The office was well in evidence at the court of the Carolingian kings and emperors, although it was not a high one. The titles of the Carolingian court were transmitted to the courts of its later imitators, the kings and princes of France. The Normans brought them to England where the royal court contained all the functionaries who had surrounded Charlemagne centuries earlier.” (Crouch, pg. 257-258)

Probably the most famous Medieval English marshal was William Marshal in the 12th and 13th centuries. Although he was a famous knight, his took his surname from his father, who had been the marshal of the English army.

So both words have something to do with war but the pronunciation is just coincidental, they're not really related.

Sources:

Martial: Select Epigrams, ed. Linsday and Patricia Watson (Cambridge University Press, 2003)

David Crouch, William Marshal (3rd ed., Routledge, 2016)