Quintin and variations are from the Latin Quintus, an adjective meaning fifth. Similarly Sexton, Octavius, Septimus, et al. The girl’s name Tess could be derived from the Greek for four (Tessares).
Max is from the superlative of the Latin Magnus.
Rex.
Also, Ray and Roy. If we are accepting more Latin and Latin-derived nouns, also Leo (lion).
Wait, are we accepting names that are nouns from any language, or do the names also have to be intelligible English words that could stand on their own in an ordinary modern English sentence? E.g. Rex does mean “king”, but very few people would just say something like “Hey, did you hear what the rex of Sweden did?”
Frank (as mentioned above) would qualify even under the more restrictive rules, since Frank comes from (and still refers to) a term used to refer to a person of Frankish ethnicity.
What about cases where there is a name that is etymologically related to a noun and also obviously related to a modern reader, but the name is spelled slightly differently than the noun in modern English? For example, Craig versus crag, Ryder versus rider (i.e. a knight), Taylor versus tailor, and Helmut versus helmet.
“William” is ultimately derived from a Germanic word for a helmet, and Charles from a Germanic word for a man.