also: やーい
interjection, suffix
hey; hey you; oi
Used when calling out to someone, often with a rough, aggressive, or teasing tone. Can be a standalone interjection or attached as a suffix to a name or pronoun (e.g., おい、太郎やい). The suffix use is somewhat old-fashioned or dialectal.
やい、そこで何してるんだ！
Hey, what are you doing over there!
おい、太郎やい、ちょっと来い。
Oi, Tarō, come here a sec.
The origin is uncertain; it may be a sound-symbolic calling-out expression, possibly related to the old interjection や.