Why do we put ress at the end of some words, like actress, mayoress and murderess, but not for others like doctress, accountantress, or teacheress?

Question

Why do we put ress at the end of some words, like actress, mayoress and murderess, but not for others like doctress, accountantress, or teacheress?

In: 12609

Answer 1

Your question has mostly been answered, but interestingly, words ending in -tor like doctor used to get -trix (yes doctrix) for the feminine form. It has mostly fallen out of use but you still see it in words like dominatrix and executrix (when drawing up a will).