Big nut

A donut is a ring of dough, yet we call it a do"nut". Curious
Say, if McDonalds were to bring out a Big-Mac which formed a single continuous loop, alternating between hamburger and bread, to follow convention it would therefore be called a big"nut".

That's the true meaning of a big nut.

You big nut. - Guy 1
Stfu, you're such a big nut. - Guy 3