Using words as stimming?

I’m a new parent to a newly diagnosed autistic son. So im

really hoping for some advice. He is 11 and has severe anxiety. 

my question is has any other parent experienced their child shouting inappropriate words? I’ve noticed when he is anxious, happy or overwhelmed he will shout not some nice words some can be swearing some can be sexual and he seems to make up little rhymes and shout them out and repeat them.

i have tired explaining that some of the words should not be used but it doesn’t make a difference. I know he has heard these words from friends at school but he is still very young minded for his age and doesn’t actually get that the words he says are inappropriate.

im at a loss of how to handle it and if it’s a common trait in autistic children? Sometimes when he is overwhelmed there is no calming the words I have to let him get it all out

thank you