Can you recommend a book that talks about the origins of the common names of plants, not just their botanical Latin equivalents?
The best book I have found is Geoffrey Grigson’s A Dictionary of English Plant Names, published by Allen Lane in 1974. It goes into a great deal of detail, and usually provides the approximate date when the name came into use. Another good resource is Flowers and Plants: An International Lexicon with Biographical Notes, by Robert Shosteck (Quadrangle, 1974).