Fun fact, a central American school for the hearing impaired actually spontaneously developed their own sign language.

I forget if it was an intentional experiment or a complete accident, but the folks running the school observed that the students developed the sign language on their own with only some personal signs older students had used prior to coming to the school as a starting point.

IIRC it’s considered a child language of ASL for that reason but it has unique grammar and words and everything.