A chemically identical dye derived from the woad plant "(Isatis tinctoria)" was used instead. Its other common names include dyer's whin, waxen woad and waxen wood. In Viking age levels of York, remains of both woad and madder have been excavated. Beginning in 1463, trade in blue dye (woad) flourished. Napoleon was forced to dye uniforms with woad, which had an inferior blue colour. In Europe woad containing the same dye was used for blue-dying. The first archaeological finds of woad seeds date to the Neolithic. Weimar acquired woad trade privileges in 1438. Towns such as Toulouse became prosperous from the woad trade. The island prospered with exports of wheat and woad. The main businesses of medieval Gotha were cloth-making and the woad trade. There has also been some revival of the use of woad for craft purposes. It has also been known as "The Woad Song" and "Woad of Harlech". The translation of vitrum as woad may date to this period. The connection seems to be that both glass and the woad are "water-like" (lat.