By Peter Bowes BBC News, Los Angeles

It all started with what Professor Paul Frommer now describes as a "fateful e-mail."

The linguistics expert from the University of Southern California is the brains behind the language used by James Cameron's 10-foot-tall alien tribe in the much-anticipated science fiction epic, Avatar.

Actress Zoe Saldana plays Neytiri, one of the native Na'vi speakers

"Jim Cameron's production department at Lightstorm Entertainment was looking for a linguist that would be able to help him develop an alien language," explains Professor Frommer.

"At that time, it wasn't even called Avatar - it was project 880 - but the e-mail was forwarded to me and I saw it and jumped on it. I was very excited about it. A week or two later I was called in for a talk."

The language enthusiast managed to persuade Cameron that he was the man to create a functioning language for a story the director had dreamt up a decade earlier.

"I spent a wonderful 90-minutes with Jim and at the end of it he shook my hand and said 'welcome aboard,'" says Professor Frommer.

The pair worked together for four years to develop the Na'vi language.

The director had already come up with about thirty words, for the characters' names and body parts. But he was looking to the professor to give the language an authentic but exotic feel.

Crucially, it had to be a language that could be articulated.

"This is an alien language but obviously it has to be spoken by human actors," explains Professor Frommer.

Professor Frommer hopes to expand the language in sequels and games

"It has to be sounds that human beings are comfortable producing."

It is a unique language, with its own syntactic and grammatical rules.

Its creator says some of Cameron's original words had "a vaguely Polynesian feel". Others have suggested that it sounds like German or Japanese.

"It certainly borrows various grammatical structures, sounds, that exist in other languages - but what I hope is that the combination in this language is unique," says Professor Frommer.

As well as creating the language, Professor Frommer taught the actors how to speak it.

"I met with each of the seven principal actors who use the language beforehand. I helped them with the pronunciation, we broke things down.

"I also created some sound files, MP3 files. I guess some of them downloaded them onto their iPods so they could listen to them at the gym."

Professor Frommer spent hours on the set, helping the cast fine tune their alien language speaking abilities.

"I gave them quite a challenge. I found that they really rose to the occasion, everybody had a great time. I knew that it had to be something that actors could deal with and handle," he says.

The language currently runs to about a thousand words. It does not have a huge vocabulary, but Professor Frommer is still working at it. He is also still trying to master his own language.

A sample of Na'vi writing

"I wish I could speak it fluently," he says.

"As for who at this point understands the grammar and such, I think probably I'm the only one. I wish that eventually that might not be the case."

In fact, one day, Professor Frommer hopes Na'vi will match Klingon, as the "gold standard" alien language.

"There's a translation of Hamlet into Klingon," says Professor Frommer.

"There are Klingon clubs that meet all over the world. There are a very dedicated group of people who meet and try to speak it.

"If anything happened like this with Na'vi I'd be delighted."