Punic refers to the people. Carthage was the name of their city, so they're also referred to as Carthaginians (see also: New Yorkers, Londoners, Dubliners, Parisians, etc.).
And their perennial rivals from Oxford are Oxonians. The English class and education systems being what they are, many in both categories will have been students at Winchester College (a "public school", which is to say an old, prestigious, expensive private school), which makes them Wykehamists. If not, perhaps they went to another public school, Shrewsbury School; its students, and people from the county of Shropshire, are of course Salopians.
England is particularly good (if that's the right word) at these but it's not alone. If you're from Buenos Aires then you're a Porteño (because it's a _port_). If you're from Christchurch then you're a Cantabrian (because of a historical association with Canterbury in the UK). If you come from Rio de Janeiro then you're a Carioca (from the name of a tribe that lived there before the Portuguese invaded).
‘Muscovite’ is from ‘Muscovy’, denoting the Middle-Ages' Duchy of Moscow and in turn descending from Latin ‘Moscoviae’.
Since English has chronic trouble mapping sounds, especially vowels, that are fundamental for Russian, ‘Muscovy’ is in fact a rather reasonable approximation. ‘Moscovia’ would be better, but alas. It's like we're seeing different fundamental colors―which we sort of do with English ‘indigo’ and Russian ‘light-blue’ (the latter being close to Newton's ‘blue’).
> Newton divided his color circle, which he constructed to explain additive color mixing, into seven colors. His color sequence including the tertiary color indigo is kept alive today by the Roy G. Biv mnemonic. Originally he used only five colors, but later he added orange and indigo to match the number of musical notes in the major scale.
So, the concept of there being uniquely-important indigo (and orange!) points on the hue spectrum were just, kinda... made up, as a bit of numerological whimsy, by Isaac Newton. And everyone else in the Western world just followed his lead, because he seemed to know what he was talking about.
I would note that no English-speaker actually seems to describe anything as “indigo” in practice. People do tend to describe plenty of things as “light blue”, though! We get taught “ROY G BIV” in kindergarten, but we basically ignore it, because it doesn’t actually fit anything else we get taught. (I don’t even recall any children’s picture books that bother with examples of “indigo” objects.)
IMHO, there’s also a much more fundamental distinction made in English-in-practice, between three kinds of green: yellow-green (“spring green”, “olive green” when desaturated), “green green”†, and blue-green (“sea blue”, cyan, turquoise.) Many people will insist that, if orange is a separate color from yellow or red, then yellow-green and green-blue are separate colors as well.
