Curd doesn't traditionally exist in (Han) China, as with most other dairy. There's a word for it now (凝乳) but it's not in any relation to tofu.
The "fu" in doufu taken by itself does indeed mean rotten. But characters on their own can have very different meanings compared to when used in combination in words. There isn't necessarily a connection, just like in English the word "rotten" doesn't have anything to do with the number 10 that's contained in it.
Tofu isn't fermented but made by boiling soy milk and adding a coagulating agent. I was curious and looked it up and that process was described the same way already in Ming Dynasty, so the "rotten" character might just be random and not have any such meaning. It's very common in Chinese that new concepts are expressed with existing characters, because you can't go around making up a new character for everything, no one could ever remember that many characters (bad enough as it is). Often it's just about the sound. For example the characters in the word for cheese (起司) mean "rise" and "manage" when taken on their own. It would be gibberish to read it that way, but every Chinese person knows combined they mean cheese.
The "fu" in doufu taken by itself does indeed mean rotten. But characters on their own can have very different meanings compared to when used in combination in words. There isn't necessarily a connection, just like in English the word "rotten" doesn't have anything to do with the number 10 that's contained in it.
Tofu isn't fermented but made by boiling soy milk and adding a coagulating agent. I was curious and looked it up and that process was described the same way already in Ming Dynasty, so the "rotten" character might just be random and not have any such meaning. It's very common in Chinese that new concepts are expressed with existing characters, because you can't go around making up a new character for everything, no one could ever remember that many characters (bad enough as it is). Often it's just about the sound. For example the characters in the word for cheese (起司) mean "rise" and "manage" when taken on their own. It would be gibberish to read it that way, but every Chinese person knows combined they mean cheese.