Ate up with someone/something phrase
Giving your attention to something or someone because you enjoy finding out about them; filled with a particular feeling.
I didn't notice that my purse was stolen as I was so ate up with the performance.
I'm sorry for not calling you back—I was ate up with a movie.
Mary has just had a new boyfriend and she is ate up with him.
From his facial expression, I can tell that he is ate up with jealousy.
The origin of this phrase is not clear.
Meaning absolutely certain or without a doubt
I am as sure as God made little green apples that Peter's the one for you, you two make a beautiful couple.