E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The colour indicates the love of truth and the truth of love. Pugin says it is used for black in mourning and fasting.
The violet on the tyrants grave. (Tennyson: Aylmers Field.) The reference is to Neros grave. It is said that some unknown hand went by night and strewed violets over his grave. Even Nero had one who loved him. Lemprière states that the statues of Nero, at death, were crowned with garlands of flowers.
I would give you some violets, but they withered all when my father died. So says Ophelia to the Queen. The violet in flower-language is emblemtical of innocence, and Ophelia says the King, the Queen, and even Hamlet himself now he has killed Polonius, are unworthy of this symbol. Now my father is dead all the violets are withered, all the court family are stained with blood-guiltiness.
This entire posy may be thus paraphrased: Both you and I are under a spell, and there is herb of grace to disenchant us; theres a daisy to
caution you against expecting that such wanton love as yours will endure long; I would have given you a violet if I could, but now that my father is killed all of you are blood-guilty. (Shakespeare: Hamlet, iv. 5.)