Reason for hand flapping in children with autism

Its called Stimming , its one of many coping mechanisms and calming self soothing ways to process whats going on or what went on , the flapping helps with calming down and slowing the thoughts down its self soothing.

Moms Expertise
it does make sence , does flap when excited also ?
    I never knew there was an actual term.. Thank you!

    I've seen MANY kids do it.. and kids without Autism.. I think and maybe I'm mistaken, but I feel like this is a way for a lot of kids to handle stress, or a social situation.. or being overwhelmed in any way.. and not have the words to express.. None of these kids (but one) have been diagnosed with autism or anything else.. But it also stopped as they got older.. So It's super interesting to know this.. Thank you...