Standard Phrase used here and there by Some People
When someone asks you to confirm something, but you don’t want to specifically confirm or deny it. Usually used when someone asks you why you are mad, and the reason mentioned is one of the reasons, though maybe not the only one.
“Why are you mad? Is this because I took your donut?” “It’s not not because you took my donut.”
Added August 2020 by amarens
10 out of 22 English speakers have heard this