sheath: [OE] A sheath is probably etymologically a ‘split stick’. The word comes from a prehistoric Germanic *skaithiz, which also produced German scheide, Dutch schede, and Danish skede. This seems to have been derived from the base *skaith ‘divide, split’ (source also of English shed ‘give off, drop’ and ski), in which case the notion underlying it would have been of a stick split open so that a sword blade could be inserted into it. => shed, ski
