David J. Peterson is the president of the Language Creation Society which specializes in the creation of constructed languages, or 'conlangs', from scratch. Peterson has worked in this field since 2000.
On 12 April 2010 HBO confirmed that Peterson was fleshing out the Dothraki language into a fully-fledged conlang for use in the series, with a vocabulary of over a thousand words. It is possible that the other languages from the later books - Skroth and Asshai'i - might receive similar treatment as the series continues.