For a man on horseback, the curved blade is a good thing, easier to handle. It’s a good weapon for a Dothrakan. But a man in full plate–shori tawakof–the arakh won’t get through the steel. That’s where the broadsword has the advantage, designed for piercing plate. -Jorah Mormont to Rakharo, Game of Thrones Season 1, Episode 3, “Lord Snow”
To me, the Dothraki arakh from the Game of Thrones is one of the weapons in the series that holds the most character–a good visual artifact that reveals a lot of information on the Dothraki way of life. It’s evidence of the Dothraki’s connection to their horses, as it does look like it is easy for a mounted warrior to wield. It’s also a good way to present the Dothraki as barbarians (at least by Westerosi standards) because it looks like a good tool for decapitation–at first glance you can tell that headhunting is not taboo with these people.
It very much resembles the khopesh, which is the Egyptian name for the Canaanite sickle-sword (sappara in Assyrian), which has been in use since the third millenium B.C. in Sumeria. The khopesh is an iteration of the earlier crescent-shaped axe called the epsilon, but is not a hacking weapon. Rather the curved blade is used to disarm opponents or hook their shields.
I plan on working on an resin replica of the Dothraki arakh, but not with a steel blade as I intend to do with Longclaw.