Rack your brain.
Rack your brain.
Rack your brain" means to think very hard or try to remember something difficult. It derives probably from the torture device, the rack, where people were physically stretched. Here, it’s just your mind doing the stretching.
I've been racking my brain trying to solve this puzzle.
I've been thinking very hard trying to solve this puzzle.
She really had to rack her brain to remember his name.
She really had to think hard to remember his name.
Don't rack your brain over it; we can figure this out together.
Don't think too hard about it; we can figure it out together.