'catheter' originates from Greek, specifically the word 'kathetēr', where the element 'kata-' meant 'down' and 'kathetēr' referred to something 'let down' or 'inserted downwards'.

'catheter' passed into Latin and Medieval Latin (as 'catheter' or similar forms), was borrowed into Middle English from these medical/Latin usages, and eventually became the modern English word 'catheter'.

Initially it denoted an instrument for 'letting down' or inserting, and over time it came to mean specifically a tube used to drain or introduce fluids into the body.