What is afemale tenorette voice?

There's no such thing as an "afemale tenorette voice." The term you're looking for is "contralto."

* Contralto is the lowest female voice type, characterized by a rich, dark, and powerful tone.

* Tenorette is not a standard voice classification. It's sometimes used informally to describe a female voice that sits somewhere between a soprano and an alto, but it's not a recognized term in classical vocal music.

So, if you're talking about a female singer with a low, rich voice, you're likely referring to a contralto.