While may most often appears as a helping verb to indicate that something is possible or allowed, it can also be a noun for a kind of shrub or small tree, also called a "hawthorn."
The may has flowers that can range from white to red, and it's also got deep red berries. Since it has a pretty flower that blooms in the spring, it's associated with the month of May. In the 17th-century poem by Robert Herrick, titled "Corinna's Going A-Maying," Corinna is gathering the flowers of the may tree, a springtime activity that goes back as far as medieval times.
