also: ごるぁ
interjection
Used to scold or reprove someone, often with a sharp tone. Common when catching someone misbehaving.
こら、そこで何をしている！
Hey! What are you doing there?!
interjection
Used to call out to someone to get their attention, often in a rough or familiar way.
こら、ちょっと待ってくれ。
Hey, wait a minute.
ちょっと can be used to get attention more politely, whereas こら is direct and often impolite.
The origin is uncertain; it is a native Japanese interjection used for calling out or scolding.