Well, you might have had a fear of something else, like having stuff sprayed on your. Fire sprinklers spew out water when there is a fire, so if you are afraid of that, you might be afraid of other things too that is somewhat related to the fire sprinklers. This is probably not known because not many people are afraid of fire sprinklers. Fire sprinklers actually save lives. It helps put out the fire in case of a fire. Hope that you can get your fear of fire sprinklers over with. It will hurt you a lot when you are an adult haha :P
Hope that helped! :)