Not that I want to be argumentative here, but how is 'lioness' a derogatory term? It's a famously proud, social animal, known for hunting down animals and protecting it's young. I don't see how that is a negative term.
As far as I know, it all sprang from 'cougars' being the term given to mid-30s women who habitually seduced members of a canadian football/hockey team (or some other sport) - that was then used as a term for women doing the same thing all over Canada and the US, and then the big-cat term just got expanded out.
I don't see 'Lioness' being a derogatory term though. Obviously 'pig', 'lizard', 'warthog', 'snake' and 'dog' (all of which I've heard as terms for men) focus on negative aspects of animals. There isn't generally a negative perception of tigers, lions (or lionesses), cougars, panthers etc - it's just a catchall term.