slang - Origin of "can't be asked"

I believe you have misheard can’t be assed for can’t be asked. In this sense, it means what UK speakers mean when they say can’t be arsed to do something. That is, that they cannot be bothered.

It is possible to construct sentences in which can’t be asked is legal, such as:

We must hide this from Mary; she can’t be asked what her part in the matter was, or she will come upon the truth.