'hyponatremia' originates from Greek and New Latin, specifically the prefix 'hypo-' (Greek) meaning 'under', plus the element 'natr-' from Greek/Latin 'natron' meaning 'sodium', and the suffix '-emia' (Greek) meaning 'blood condition'.

'hyponatremia' developed as a modern medical coinage combining Greek/Latin elements: Greek 'natron' became Latin 'natrium' (the source of 'sodium' and 'natr-'), and medical New Latin/English formed 'natremia' with the suffix '-emia'. The British spelling variant 'hyponatraemia' has the same roots and meaning.

Initially, the components referred to 'under (hypo-) sodium in the blood' and over time this compound has retained the medical meaning of 'abnormally low sodium concentration in blood'.