for the life of {sb}
1
used when one is incapable of understanding or remembering a particular thing
The origin of the idiom "for the life of someone" is unclear, but it has been used since at least the early 19th century. It likely evolved from earlier expressions in English that emphasized the importance or difficulty of preserving someone's life. This expression is used to express a sense of frustration, puzzlement, or inability to accomplish a task or recall information, especially when trying very hard.
- He couldn't remember the name of the movie for the life of him.
- I couldn't find my keys for the life of me.
- She couldn't figure out how to use the software for the life of her.
- They couldn't locate the source of the noise for the life of them.
- We couldn't understand the math problem for the life of us.