having no way to deal with something; at a complete loss
Rare fixed expression meaning one is utterly unable to handle or manage a situation, with no options left. Literally 'can neither hold nor lift'.
この難問にはもちもさげもならぬ。
I am completely at a loss with this difficult problem.
The historical derivation is uncertain; the phrase literally means 'can neither hold nor lift', figuratively expressing helplessness.