The term OSIER is a type of WILLOW tree, also known as a withy. It is a species of shrub or small tree that is native to Europe, western Asia, and North Africa. The bark of the osier is used for basketry and other crafts, and its branches are often used for wickerwork and fencing. The term osier is derived from the Old English word 'wísa', meaning 'WILLOW'. The term withy is derived from the Old English word 'wíðe', meaning 'flexible twig'.