"plain jane"

does anyone know where the saying "plain jane" originates from? Is it from Jane Eyre by Charlotte Bronte?

Two different dictionaries offer first uses, but both in the 20th century. See dictionary.com

The Oxford English Dictionary cites it from 1912. Jane Eyre seems a very unlikely source. "Jane" is not infrequently made to do duty for the generic female, as in "Jane Doe." "Jane" makes a useful counterpoise to "John," also not infrequently made to stand for a whole gender, even a whole population, as in "John Q. Public."
SS

And it just happens to rhyme with 'plain'. 'Plain Annabel' wouldn't really work, would it?

DFG