It's been driving me nuts for days and some of the threads in this forum have been reminding me of it all the more. I don't know if it was a novel, a novella (in a collection) or a short story from an anthology.

It is set on a future Earth that has been enslaved by space-faring aliens.

The humans are controlled by an overseer called, IIRC, "Par Shavorlem" who is needlessly cruel and drives his human slaves to the brink of death.

He's also perverted - owing to differences in physiology, their mouth/feeding parts are hidden under one of their appendages and they have evolved a societal taboo around them. Par Shavorlem keeps a human female as a pet and gets off on seeing her speak with her (brazenly exposed) mouth. The humans try to do what they can to get rid of Par Shavorlem and the ending of the story is quite interesting.

I cannot, for the life of me, recall the name of the story or its author.

If anyone can help identify it so I can track it down, it would be most appreciated.