I am writing a middle-grade series where a character is introduced early on as a supporter of the protagonists. He is enthusiastic at first, but grows more and more pessimistic as he realizes that the protagonists have basically no chance of winning and have a good chance of dying. Due to an incident in his past, he cannot accept taking deadly risks, thinking of people who do as a mixture of brave and stupid (but mostly the latter). Eventually he gets so fed up that he joins the antagonists, figuring that it will raise his chances of survival. The thing is, I don't want his change of allegiances to be obvious to the readers before it gets revealed. I'm trying to make him seem pretty harmless: he's very nerdy, quite a bit cowardly, pretty nice (albeit sarcastic), may have a little crush on one of the protagonists' allies (well, until she dies), and has a habit of talking a lot at a very fast pace. However, he is a geneticist, which might make some readers suspicious, even without the name. And I don't want readers to think I don't approve of genetic research: I think it's pretty cool. Now, onto my main concern: his name. Since he's Icelandic, I went through the list of approved Icelandic male names and picked Sindri. I really like the way it sounds, but I'm afraid that readers might read the name a little too closely, realize that it's spelled Sindri, and realize that he is not a trustworthy character. Should I change the name? I'm getting all attached to the name, and I don't want to change it, but at the same time, I don't want to be one of those authors who thinks they've done a surprising twist, only for the readers to have seen it coming from miles away. (Y'know, like Callaghan being the bad guy in Big Hero 6. Did anyone else go, "Yeah, he's evil," five seconds after he was introduced? XD)
Honestly, when I saw the title for the question, I thought that the whole name was an allusion to this fact (in that either the name was a reference to a character or the name's meaning in it's native language was a reference) and not that the word "Sin" was contained in the name (the name sounds like it's Hindi or Indo-Persian, but that's speculation on my end, so it took me a while as I was trying to remember my limited knowledge of Hindu pantheon and even more limited knowledge of Indian media characters and tropes). Unprompted, I didn't see a problem with the name, and thought it unusual.
It's not unusual for characters to have symbolic names and subvert expectations. Consider the villain from the "Gargoyles" Series, MacBeth (I've been rewatching lately so it's on the top of my mind) who shares his name with the titular play by Shakespeare that should not be named, but he's presented as only sharing a Scottish accent with the character at first, and any reference to is brief (In his first episode, the similarity came up, but it has nothing to do with the conflict... the big "reveal" is that he has a very personal relationship with another villain who isn't in this episode and even then, that requires knowing a line by the other villain that was uttered 4 episodes prior to understand the full implications.). And all of this requires the kids watching the show to have some knowledge of Shakespeare to begin with, which is a little above the reading level of the kiddies (though many original fans are fans of the Bard because of this show).
There are multiple things you might consider, which could counter your theory of 'Sindri' being an obvious 'bad guy'... And that it's a bad thing.
1: 'Sin' isn't called sin in all languages, so a translation of your work would already make it less obvious - Unless, of course, people actually pay more attention to the English-sounding part of the name then...
2: It differs from one person to another if they mind suspecting a person of 'turning' or 'being evil' from the moment they're introduced. I've heard and read somewhere (sorry, no source this moment) that some people actually enjoy a movie/book more once they "know" what's gonna happen - I've yet to feel that way myself, though.
3: Having a character disagree with the protagonist's plans and motives is completely natural, even for characters 'on the same side' of the 'struggle'. I wouldn't assume that many people would predict it.
So, all in all, this is a case of 'your mileage may vary', meaning that not everyone will have the same opinion of it, and still, a lot of people might not notice it at all.