Looking up the meanings of names used in the Harry Potter story was one of the things that made me aware of how much effort J.K. Rowling put into the details of her story.
One common flower name that has a lot more connotations than you might think is Lily – which was the name of Harry's mother.
The flower Lily, and hence also the name, commonly represents purity, innocence, beauty, death and majesty. In the Church, the Lily is used as a symbol of the Virgin Mary. The fleur-de-lis, a stylized design of a lily, is a common symbol in heraldry (particularly associated with the French monarchy), for example in coats of arms.
"Other folklore tells of lilies, unplanted by any human hand spontaneously appearing on the graves of people executed for crimes they did not commit. Some believe that planting lilies in a garden will protect the garden from ghosts and evil spirits. In China, the day lily is the emblem for motherhood. To dream of lilies in spring foretells marriage, happiness and prosperity; to dream of them in winter indicates frustration of hopes, and the premature death of a loved one."
Furthermore: "Long ago, Spaniards believed that eating a lily's petals would restore someone who had been transformed into a beast back into human form."
It is tempting to believe that Rowling knew about this. In his third year at Hogwarts, Harry learns that his father James was an Animagus; that is, he could magically transform himself into an animal (a stag). In his fifth year, through the magic Pensieve, Harry learns less flattering things about his father: "Judging from what he had just seen, his father had been every bit as arrogant as Snape had always told him." (OP28) Yet, as James grew older, he seems to have shaped up under the influence of Lily, and stopped playing cruel games just for fun.
James, by the way, is the English version of the Hebrew name Jacob, meaning: "He who supplants." Supplant means "take the place of". Jacob in the Old Testament outsmarted and took the place and birthright of his older twin Esau. Seen from the perspective of additional things that we learn in the 7th book about Lily's early life, it could perhaps be said that for her, James (in a way) came to supplant Severus...