Mark Handley, born in Hollywood, California, was a writer, screenwriter, and playwright. He got married and then lived in log cabin with his wife to live in isolation.  He wrote a play named "Idioglossia," which became a (1994) film named "Nell," starring Jodie Foster Liam Neeson Natasha Richardson and Richard Libertini
. It was directed by Michael Apted, and Mark Isham, provided the music.

Didn't Amy Farrah-Fowler have her own secret language?  There was a very well known Brit who I remember telling the story of having a secret language in which he and his sibling would converse during train journeys, while listening to peoples' remarks about "foreigners" and at the end of the journey they would tip their school caps and say "goodbye" to their fellow travellers in perfect English.  I cannot for the life of me remember who it was.  I thought it was Michael Bentine, but I can find no mention of it online.

Incidentally, Michael Bentine, what an interesting bloke he was over and above the stuff everyone knows and remembers about him.  en.wikipedia.org/wiki/Michael_Bentine

Just killing time between unloading my groceries and the footy starting. 

That's funny, we always called it Spanglasi.