Next, Mr. Peterson tried to establish words that would be native and basic (meaning they are not derived from another Dothraki word), toying with letter combinations and sounds he liked. His favorite sound is "JH" as in "genre," so he made the word for man in Dothraki mahrazh.
After he amassed a small vocabulary, Mr. Peterson tested out basic grammar. He adored the 18 noun classes in Swahili and the negative verb forms in Estonian, both influences in his created languages. He scribbled sample sentences and added suffixes and prefixes to expand the vocabulary.
He aims to eventually expand Dothraki to around 10,000 words - or about the equivalent of college-level foreign language proficiency.