Oy Definition
oi
interjection
Used to express surprise, pain, grief, worry, etc.
Webster's New World
An exclamation typically expressing mild frustration or expressing feelings of uncertainty or concern.
Wiktionary
Origin of Oy
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Yiddish אוי (oy, “oh, oy”)
From Wiktionary
Yiddish
From American Heritage Dictionary of the English Language, 5th Edition