a dinni ken
A dinni ken is like saying you're clueless and you're not even trying to hide it.
'I dinni ken where my shoes are.', said by a kid who left them in the hallway last week.
'I dinni ken why I'm grounded.', said by a kid who forgot to do his homework three times.
'I dinni ken what this means.', said by a kid who just looked at the test and cried.