1
general::
1. Also, for all that. In spite of, notwithstanding. For example, For all her protests she still loved the attention, or He's too old for the part but he did a good job for all that. [Early 1300s] 2. for all one cares or knows. So far as one knows; also, one doesn't really care or know. These phrases are employed like a negative. For example, He can buy ten houses for all I care, meaning one doesn't care at all, or For all I know she's gone to China, meaning one doesn't really know where she is. [Mid-1700s]
American Heritage Idioms