OK, I just wanted to point out that, while early experiences can leave you with a conditioned negative response, and that's legitimte, it's not an actual phobia. Phobias are completely irrational, and usually not experience-based.
This which is a thing that is true.
I work as a tour guide in a gold mine that was abandoned in the 1950s and has been repaired to take folks underground and see the old workings. Sort of like a highly unusual museum all about mining and the Australian gold rushes. And because we go down over 60 meters (about the height of a 20-storey building) into very old tunnels deep underground, where it's dark and cramped... well, I get a lot of people who just sort of freak out. But you get it for a whole bunch of reasons - some folks hate the dark, some hate the loud machinery, some hate the fact that they're underground, some hate the tight spaces, it all varies. But generally there's two categories that I fit people into.
There's your
Rational Fear people who are scared for intelligent reasons. They've heard horror stories about mine cave-ins, or they suspect the ground is unstable, or they don't trust that rock-crushing machine I'm using, or they aren't convinced our reinforcements are up to scratch, or whatever. These people can mostly be calmed down if you just point out that it IS safe, otherwise we wouldn't be taking tourists down there. I explain how the reinforcements work, and how mines aren't nearly as dangerous as the old stories make them out to be, and they can over come the fear.
Then there's the
Irrational Fear people. They don't have an intelligent reason to be scared. They understand that obviously we take away as much risk as we can, and that the danger is incredibly slim, but despite knowing that, they can't deal with it. In some folks it's actually a reaction to the change in altitude, air pressure, oxeygen levels, light, etc. that comes from being deep underground, which causes a genuine physical response that makes them have a panic attack... and in other cases, it's just straightforward claustrophobia, or some other phobia, like small kids scared of the dark or loud noises.
I've seen toddlers laughing and giggling at a cast-iron rock drill as it carves through the stone, and I've seen big burly macho men who freak out when I blow out a candle. Every kind of fear is subjective. But genuine phobias are ones that don't have a backstory, or an explanation, or anything to justify it. It's just a fear that you cannot control.
And since it's the topic... I have no real phobias that I know of, though I do have an irrational hatred of ventriloquist dummies. No joke, the creepy little fuckers just give me chills.