I think mine comes from my mum being a blardy awful cook, to be honest. The number of foods she made a pigs ear of is shocking. So in her house, you were glad to get random-whatever-from-iceland and chips, it was an improvement. Nothing ever tasted nice, so I have ended up with some really weird taste buds, I love spicy food and things with really strong flavours but anything I would consider slimy, nope. And for me I think a lot of that comes from being repeatedly fed things like really cheap sausages, braised (badly), or poor quality slightly slimy chicken, or generally cheap shit food.
I am a LOT less fussy than I used to be - I wouldn't touch lamb, pork, fish (well, unless battered!), pretty much any veg, porridge (she made that taste VILE), mash or boiled potatoes, plus all the things I still don't eat. I'm working on it in my own way.
I'm gradually adding things BUT, if I am going to try something new I am only comfortable doing it on my own, or with DH. I find my inability to eat certain foods embarrassing enough as it is. So I would actually be highly unlikely to try something new at somebody elses house, because if I don't like it it is quite possible I will struggle to even swallow it which would be humiliating for everybody. It's not a case of "getting over yourself" as some people have said.
For me, there is a difference between something I maybe don't really like the flavour or taste of, but can "choke down" and things where I simply can't eat them. But, bizarrely, although I think it originates in childhood for me it is not limited to foods I experienced as a child. I think it has left me inherently suspicious of foods and with massive issues with texture which extend to foods I have never tried.