I hope that you do not find this question offensive. This is my first time here, and I do not wish to be impolite.
One of my co-workers recently declared, "The real problem is that she doesn't know jack shit about this issue." What could this possibly mean? He tells me that this is a common expression where he comes from (Midwest USA).
I am thrilled to find you!

Jack shit dates from the 1960s, is a US coinage and means 'absolutely nothing'; it is always used with a qualifying negative verb, e.g. 'you don't know jack shit about...' It combines the slang words 'jack', meaning very little, an infinitesimal amount and 'shit', in this context meaning nothing, typically in the phrase 'not worth shit'.