'sheathe' originates from Old English, specifically the verb 'scēaðian' (and related noun 'sceað'), where the root 'sceath' meant 'covering' or 'sheath'.

'sheathe' changed from Old English forms into Middle English (e.g. 'shethen'/'sheathen') and eventually became the modern English verb 'sheathe'.

Initially, it meant 'to put into a covering or sheath'; over time this core meaning has largely remained, now often specifically 'to put a blade into a sheath' or more generally 'to encase or cover'.