Discussion Forum—A Way with Words, a fun radio show and podcast about language

Welcome to the forum. A great place to find the answer to this type of question is: http://books.google.com/ngrams/

There I found "administratrix" still in use, with a peak in the 1800s.
Only a single hit for "testrix" (which I'd never seen before).
And "aviatrix" peaking in 1940, with a decline in the 1960s, but apparently also still in use.

I'd have guessed all those terms would've been phased out with the rise of the women's movement in the 1970s. I have to say I rarely hear/see these terms these days.

Interesting the common thread that seems to link the non-gender-specific words in that list.

Several of them pertain to long, skinny animals like snakes, eels, or worms. Not sure what that means.

A couple others relate to scars (hmm, reminds me of the randy country girl who offers to "show you where the horse bit me").

Matrix is actually rather interesting. It comes from an OE/ME word, "matris", which means matron, or the feminine of master.

Another reason I found it strange is that the ess suffix seems to have stuck around. For example hostess and priestess, but the only modern example of the trix ending I can think of that is still used is dominatrix.