What is the correct niqqud to put on the name of the מהר"ץ חיות? Wikipedia claims that his last name is spelled Chajes in English, and that Chayes or Hayot may also be seen. This seems to imply that the correct niqqud should be חַיּוֹת hayoth (a word which can refer to angels). On the other hand, when I encountered the name I had always blindly assumed that it was חִיּוּת ("vitality"), and the same spelling could also be חַיּוּת ("vitality"). Are any of these vocalizations correct? Alternatively, is his original last name a non-Hebrew word pronounced /χajəs/ (in IPA) that was identified with a Hebrew word with niqqud just a folk etymology, and therefore it might not have a "correct" vocalization?
"Chajes" is not the English version of the name, but the German version, which would point to a pronunciation of "חַיֶס". In Hebrew, though, there's a vav, which it seems was pronounced as a cholam. But I can't find any explicit evidence for this.
If you look at his Iggeres Bikores republished in 1853 by Jacob Brull, you'll see the German version "Chajes" on the cover page. (He was still alive at that time and even wrote a short preface to this edition.) More interesting, though, is the sentence in Brull's preface in which he makes a play on Chajes's name. He writes: "ולי מה יקרו אמרות איש בריתי, חיו״ת הנה", in which he's clearly referencing Shemos 1:19, which has the nikkud: חָיוֹת. Now, being a play on the name, it needs to be taken with a grain of salt, but we can assume that that was at least similar to what his name sounded like.
Besides for that, I can't seem to find any source that has explicit vowelization for his name or would make it clear what the correct pronunciation was. As a side point, I'm pretty sure his grandson Tzvi Peretz Chajes pronounced his name "Chayot", but now that I look into that, I can't find a good source for that either. If I find anything else, I'll update this post.
I have usually heard the name pronounced as stated in the Wikipedia article, especially in academic settings. Whenever I hear the pronunciation like 'khee-us' I assume that it's because people feel uncomfortable giving an achron a last name that can mean 'animals'.
A few people have speculated over the origin and meaning of the name. One source that I can link to is an article on name from [The Jewish Quarterly Review vol. 10], where the theory is proposed that it comes from the woman's name 'Chaya'. Regardless of the theory though, the author was confident that this is the proper way to pronounce this Eastern European surname.
I heard Rabbi Yitzhak Yosef and his father Rav Ovadia z'l pronounce it "Maharatz Hauyt"