When creating Dothraki (and later Valyrian) for the series, showrunners turned to creative linguist David J. Peterson, who turned the few scattered words and phrases invented by George R.R. Martin, and extrapolated them into detailed, functional languages. This has been invaluable for creating a sense of realism in the show, but there have been a few hiccups along the way.

In one of the early scenes portraying the Dothraki, Jason Momoa's Khal Drogo watched two horny Dothraki braves fight to the death. Producers told him to ad-lib a line, so Momoa used a refrain from the Maori haka war dance: i te waka, or "in the canoe." It wasn't initially subtitled, but Peterson liked the sound of the line so much, he ended up retconning it into the Dothraki language as "Itte oakah!" or "Test your mettle!" The invention of the word oakah in this way would go on to influence how Peterson wrote Dothraki lines throughout the series.

Iain "Jorah Mormont" Glen got into the action as well, when producers forced him to ad-lib a Dothraki line at the last minute. The producers realized they needed Jorah to holler "Take all the gold and jewels!" in Dothraki, so they sent Peterson an email requesting a translation. Trouble was, Peterson was asleep — when he woke up and emailed them the correct translation ("Fichas ei hoshor ma dan!"), the scene was already filmed. The moral of the story: sleep is stupid.

Months later, a producer noticed the discrepancy between the line Peterson provided, and the actual sound of Glen's line — Peterson realized he would need to supply a Dothraki transliteration and translation for the nonsense babbling Glen had improvised. After some effort, Peterson paired Glen's gibberish with a plausible Dothraki expression: Mas ovray movekkhi moskat, or "The loose valuables are for loading." That doesn't have quite the same ring to it but, considering what he had to work with, that's pretty impressive.

Besides, since Jorah Mormont speaks Dothraki as a second language, it only makes sense he'd occasionally say something awkward. We don't really understand Peterson's work or how he does it, but we're glad he's being paid well for all this.