Best I can figure, Columbus called it “Santa Cruz” (“Holy Cross”) when he landed there. It changed hands a few times, and by the time the USA annexed it it had become “Saint Croix,” which is stupid, because a) “Saint” is an English word and “Croix” is a French word; b) although neither French nor Spanish differentiate between the adjective “holy” and the noun “Saint,” English does. So basically we’re pretending there was a saint named Croix. There wasn’t.
“Saint” is a French word. “Saint Croix”, translated to English, means “Holy Cross”, just as it is “Santa Cruz” in Spanish.
Although it may seem weird to an English speaker I’m sure there’s nothing weird about it to a French speaker. Remember that English got the word from French, we’ve just twisted the meaning away from the original slightly. If anything is stupid, it’s the way we use it.
Wouldn’t that be “Sainte Croix” (in French) ?!?
I mean, whatever language “Saint Croix” is supposed to be in, it damned well isn’t French.
No, because Croix is masculine.
I would like to see a dictionary reference for that. Is it somebody’s name? Where have you ever seen Croix be masculine, besides in the very name in question? How do we know the English name does not derive from Dutch or Danish?
For the same reason English-speaking football fans call the German football team Bayern Munich, not Bayern München or Bavarian Munich.
I just checked in 2 dictionaries, and the French word “croix” is feminine, so in French it should be “Sainte Croix”.
And the same place name is spelled that way in other French speaking countries. The OP is correct it is a combination of both the English and French word, which does change the meaning. I don’t think there is any logic to it.
Langenscheidt says masculine. Hmm, maybe ze Germans are wrong.
The English-language names for various foreign names are inconsistently translated. I just learned that the city in Spain that we usually refer to as Seville is spelled Sevilla by Spanish speakers (and appropriately pronounced). There are a number of recent cases where the usual English-language name of a foreign city has changed to be something closer to the native pronunciation.
There’s a number of city names on the continent for which English usually uses the French spelling, even though the language used there isn’t French. Seville is one; Rome, Turin, Milan, Naples, Brunswick, Cologne, Munich, Nuremberg are others. Vienna, is sort of another, but we modified the French Vienne slightly. There’s others; this isn’t an exhaustive list.
I suspect this is something to do with increasing ease of communication and travel and a wider knowledge of foreign languages and countries. Where there were old-established trade links, but communication was mostly in writing, the names of foreign places would have got a bit mangled, and that stuck. But for places that became more widely known later (from about the early twentieth century onwards), people knew enough to adopt something closer to the native pronunciation and spelling. It might also have something to do with frequency of contact. Places like Paris, Rome, Florence, Venice were always so frequently mentioned that the old mangled pronunciation survived from sheer force of habit. But, for example, once the numbers of the British upper crust visiting Leghorn fell away, it became more usual to refer to it (for the few who needed to) as Livorno.
Whether that was to show off their knowledge or it was considered better manners to do so could be a matter of debate.
Yes, English got lots of the weird pronunciations via French.
The worst change IMHO is Genoa, which requires multiple vowel transitions. The original Genova is more euphonious in both Italian and English.
True, but I was only talking about spellings. We don’t pronounce most of those names the same way the French do.
You can’t blame that spelling on the French; it’s spelled Gênes in French.
A couple more additions to my list are Prague and Lucerne.
I think Leghorn as the English name of Livorno beats that.
Croix is definitely feminine. There is a Sainte Croix (abbreviated Ste. Croix) in Quebec.
You mean a city in España? 
That scene in The Exorcist. Where it’s doing the penetrating.
Too soon.