I'm presuming that is how you spell it - rhymes with a Scottish word for poo, so that is my best guess as how you would write it down. Six-year-olds are not very forthcoming with details of the mundane type.
Anyhoo, I had always thought that the language-inventing was a multiples thing until I had a bizarre conversation with one of Youngest Hobbit's classmates today.
Seems he has introduced my boys to his world where everyone is classed as Dobbys, but only if you are good and a friend of ETs, well a friend today at least. So Eldest Hobbit is in Dobby world a 9-year-old Dobby, but in Dobby language that is said as nine hundred and ninety-nine.
"Aha," says me acting like I have a clue, "So then if you were a 7-year-old Dobby you would say seven hundred and seventy-seven."
"No," says ET looking at me as though I am some kind of idiot just arrived today, "it would be four hundred and eighty-two."
His grandmother explained that this is something ET and his older brother had made up, including a Dobby language. The Hobbits went through a year of speech therapy to encourage them to communicate with other people, and to speak English; their idea of communication was to teach their friends their language when they first went to pre-school nursery.
I have a list of their words, for when they are older, see if they remember any of it. (one of my favourites was when they were about 18 months old they would call dogs "puppy gone big." They could say dog alright but no, it had to be puppy gone big.)
Now where did I put that nosgabby, oh right, it is over by the gabbygab.