1.The oldest usage for this term was actually an empowering one for women, it was a term of endearment for the Goddess, without which life could not have been created. She was the mother(
breeder) of the human race.
2. Then applied to
female dogs used to breed, then for any female dog, whether breeding or not
3. then applied to women to demean us to the ranks of a dog.
4.More recently it applies to women in
power(Again deriving from the use in connection with the Goddess, but usually used derogitorily by men who feel emasculated by the women who break through the glass ceiling).
5.It is also a term for someone riding on the back of a motorcyle.