Special Words For A Baby When Someone Is Autistic And Mute, How Can They Still Say A Few Words?

When someone is autistic and mute, how can they still say a few words? - special words for a baby

I am a high school student. I work with students with special needs. He is a student with autism who can speak some simple words. Why is this so?
I worked with this student for a while. It is quiet, but you can say a few words .. Today, he said words such as: baby, ball, foot, uh-oh. commonly used sign language, but.