Short phrase, used to threaten the listener of the speaker into not doing something they've just spoke of. Similar to don't you dare, but it more accurately translates to "if you go and do said thing, I will make sure there are consenquences".
Speaker 1: I am going to tell your mum about what you just did!
Speaker 2: Etsi kai!
Speaker 1: What will you do? Deny it?
Speaker 2: Etsi kai!
Speaker 1: What will you do? Deny it?
by Hmanasou23 July 28, 2021