We need answers.

Jennifer Aniston celebrated her 52nd birthday on Thursday, and we, too, celebrated Jennifer Aniston's 52nd birthday.

It was an emotional rollercoaster of A-list tributes — from Justin Theroux to Reese Witherspoon. Aniston's best pal and former co-star Courteney Cox also shared the birthday love, posting a pair of throwback photos from their decades-long friendship, one of which included Cox's daughter Coco as a small child. 

Cox's true gift wasn't to Aniston though — it was to us. In the caption of her Instagram, the Friends alum revealed Aniston's mysterious nickname. 

"Happy Birthday Jenny Louise!" Cox wrote. "We've known each other so long I don't even remember why I call you that. I love you !"

We're also coming up empty on this one, but hey, it's catchy. Don't worry, Court, we're on the case. Instagram will not rest easy until we know why Aniston's nickname is "Jenny Louise."