The kessi (phonetically, kishie) of Shetland and the caisie of Orkney is a twined back basket usually made of straw and common rush (Juncus effusus). Other plants were used, especially marram (Ammophila arenaria) and dock (Rumex longifolius). The tradition, unique in the British Isles, was a consequence of the local ecology, where there were few durable materials for basketmaking, as well as a dearth of timber. Baskets were used to carry a multitude of things – especially peat – and they were used on the backs of packhorses, or borne by humans. The name kessi is a reflection of the Norse heritage of the Northern Isles and comes from the Norwegian kjessa and Icelandic kassi.