Recently my work supervisor asked me whether I knew what 'milking parlour' meant. She thinks it could be a euphemism for some sort of tax dodge or other criminal activity. We don't even use the term 'milking parlour/parlor' in Australia – it's a cow shed! I was wondering whether you and/or your readers would have any idea.
I haven't been unable to unearth anything except the obvious "shed or building specially equipped for milking cows" (OED Online). Nothing about tax dodges or criminal activities, anyway.