for the life of Idiom
for the life of me
it is a mystery to me, why in the world For the life of me, I don't know why she stays with him.
for the life of one|for|life
adv.,
informal No matter how hard you try.

Used for emphasis with negative statements.
I can't for the life of me remember his name.
for the life of one
for the life of one Although trying hard, as in
I can't for the life of me remember his name. This expression is always used hyperbolically, that is, one's life is not at all endangered. [Late 1700s]
for the activity of (one)
Despite one's best efforts; to any amount whatsoever. Often acclimated in abrogating constructions. For the activity of me, I can't bethink area I larboard my keys! She couldn't accept for the activity of her why bodies were so bedeviled with celebrity gossip.Learn more: life, of for the activity of (one)
Though aggravating hard: For the activity of me I couldn't bethink his name.Learn more: life, of