Re: Have I got this right?
I think you don't mean "audio description", because that is a voice explaining what is happening on screen, for blind people. I presume you mean subtitles ("closed caption") or on-screen sign language.
Your friend might be interested in this week's "Fry's English Delight" with Stephen Fry, but utterly frustrated because it's a programme on radio. Except that there is an English transcript (this time only, I suspect). Both are here https://www.bbc.co.uk/programmes/m0007wv2
Anyway, it's about the history of sign language, and how it is nothing to do with English at all actually. Apparently this is Series 10 so a lot of subjects have been done, and at the same time "Word of Mouth" and "The Verb" are mowing the same lawn... you see we even run out of metaphors.
According to this, if you have a deaf friend then you have a sign language nickname. Donald Trump has a celebrity one. Madonna's is intriguing because I would have thought she was famous enough to have one already before... that...