Where does the term "shrinking violet" come from?

I know there had to be something prior to the DC comic character. Is it just common usage for a shy person or is there another origin?

Where does the term "shrinking violet" come from?
http://www.phrases.org.uk/bulletin_board...
Reply:shrinking violet noun [C] INFORMAL

a person who is very shy or modest and does not like to attract attention
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