oi · interjection, noun1
Variant of the interjection hoy with h-dropping in working class and Cockney speech; first recorded in the 1930s. Compare also unrelated Portuguese oi and Japanese おい (oi).
oi · interjection2
Variant of oy, from Yiddish.
oi · interjection3
Borrowed from oyez, 2nd person plural imperative of the verb oir (“to listen”), as used as an interjection in duplicated form “Oyez, oyez” by public speakers of medieval times to draw attention before a public address; see oi oi.
Etymology from Wiktionary, CC BY-SA 4.0.