I'm honestly baffled at the comments about this name sounding like 'anus.' It's Agnes without the 'g.' You don't pronounce Agnes like 'Ayg-nis' so why would Annis be 'Ay-nis'?
My name is Annis. Pronunciation can be a problem. I usually say, "Pronounced Annis, like the spice." For some, that doesn't ring a bell, so I say, "Rhymes with Janice." And yes, I have been called anus. Usually only once. Except for that unthinking car salesman who didn't get my business.