ουστ

Etymology
Possibly from or only the latter  likely with multiple dialectal variants leading to the 🇨🇬.

Highly likely, some kind of onomatopoeic sound, possibly conflated with the Turkish term. Compare 🇨🇬, 🇨🇬, 🇨🇬 and 🇨🇬, all onomatopoeic used to shoo an animal. For a similar phenomenon see 🇨🇬, 🇨🇬 and 🇨🇬, all likely onomatopoeic from the sound used to attract a cat.

Interjection

 * 1)  shoo used to get rid of animals and undesirable people