I’m glad you asked this question, anon. 

To me, and I think to most people who actually have negative physical and psychological responses to certain things, “trigger” is for something that causes really distressing thoughts and reactions that either start a panic attack or give me symptoms of panic (like tension in the chest, fear, obsessive thoughts, guilt, impending doom, and things like that). So I don’t feel bad about saying “humming is a trigger of mine” because if I hear another person humming a tune I will start to have a physical and psychological response to that. I may not actually have a panic attack, but I do need to breathe deep and do what I usually do when I feel panic coming on. 

But for something I’m just not comfortable with for whatever reason, “squick” is the term I use. You’re right when you say that fandom circles to tend to associate “squick” with kinks you’re not into, but I don’t think there’s anything wrong with using it for non-kinks. Like, if I say I’m squicked out by student/professor relationships (except in roleplay) then that just means I’m not comfortable with those and would rather not read them. There isn’t anything wrong with that. To my understanding, “squick” is supposed to mean “I’m not comfortable with this” and you don’t have to justify why that is to anyone. You don’t have to explain your level of comfort or why it makes you uncomfortable, all you have to say is “it squicks me” and that should be enough. 

The issue with saying that something is a “trigger” when it isn’t is that it muddies the line between “this makes me uncomfortable and I’d rather not deal with it” and “this causes me actual distress and spurs negative reactions I cannot control”. Because here’s the thing, a person can put their squicks aside at times. A person can ignore mild discomfort, and might actually grow to like something that once squicked them (I think of A/B/O for this because a lot of people I talk to were initially squicked by A/B/O and changed their minds.) Triggers are much harder to overcome and they require a lot of work, dedication, and therapy to get to the point that they no longer bother a person. And sometimes a person will never get over a trigger. Sometimes a person needs to voluntarily and safely expose themselves to the trigger in order to get past it, sometimes they just can’t and they have to learn to live around that. 

So, my advice to you is that you use “squick” for things that make you uncomfortable but don’t cause severe physical and psychological distress and to explain to people who ask (if they ask (side note: I don’t think they should because what you don’t have to justify what you aren’t comfortable with to anyone else)) the difference between the two terms. “Trigger” is a strong word with strong connotations and should not be taken lightly. And, if that word doesn’t feel right, you can always say “I”m uncomfortable reading about X” and that should be good enough for anyone who asks. If it’s not and they want to give you shit about it, tell them to bite you. (Or send them my way, I’ll give ‘em what for.)