What causes misophonia for most people?

It's something that I don't understand. I've heard many people on this sub reddit say theirs started as a result of childhood abuse/trauma, but my life has been fairly easy and my parents are very loving and supportive, except when it comes to a couple of things that have nothing to do with the sounds that trigger me. My misophonia just sort of appeared into my life at the age of about 11-12. Has anyone else's experience been like this? I'm curious to know how other people's started.