Well, I can hear her humming like a duchess in heat

The story:

I was singing with this song at a party. My cousin, who was a life-long Ozzy fan, turned around and looked at me with a bright red face, like he was about to burst into laughter or tears or both. I said, "Well, what is Ozzy really saying there? He could be talking about a duchess. He's English, you know." But it didn't help. I had made a fool of myself in front of him, and in front of his friends who were listening.