It is stated here:
his brother Donal's favourite conversation-starter in the pub: ''Artemis Fowl is based on me.''
''So I took this character, my brother Donal, the little 12-year-old Bond villain, and said, 'What if he kidnaps one of the leprechauns for the crock of gold?''
So apparently, Artemis is based on Colfer's brother Donal.
We know very little about the linguistic construction of the Gnommish language. Eoin Colfer is no Tolkien; his novels are valuable more for entertainment than for deep and complex worldbuilding.
Gnommish is a spoken language. In-universe, it's not just an enciphered version of English with fancy letters, as the other answers here claim. The fact ...