Why is Nana called pp?

This is a part of Ye Weiyang:

He (Liu Ye) shouted at me (Nana): "Ha, what should I say when I win the lottery?"

"Thank you PP!" I patted him on the face and said. PP is his nickname for me.

On the day he received the award, because it was exclusively broadcast by cetv, I specially booked a room in the hotel and stayed in front of the TV with his parents and sisters. When he lifted the golden horse, he said to hundreds of millions of audiences across the Taiwan Strait and three places, "Thank you, my girlfriend PP!" I was crying and laughing. For the first time, I feel that there is a kind of happiness in life, that is, even though we are separated from Wan Li, he can still recognize you, and he keeps every joke in his heart. This is the happiness I want.