Elves were once Pucks, taken at birth by arrogant nobles into slavery.
Since Elves have no gender, they are often given one by their master, who will dress them in britches or a dress depending on preference.
All slaves, regardless of species, are branded for identification. This mark is usually in the form of a permanent tattoo, and is somewhere noticeable like the face or neck.
As a way of separating them from their people, Elves usually have their hair, ears and tail cut down to remove their identity. Many Elves have never mingled with their people, and removing these traits, slavers feel, will prevent them from going into hiding in the Greenwood.