'balneal' originates from Latin, specifically the word 'balnealis' (from 'balneum'), where 'balneum' meant 'bath'.

'balneal' changed from Medieval Latin 'balnealis', which in turn comes from Latin 'balneum' and Greek 'balaneion' (βαλανεῖον), and eventually entered English as 'balneal' via Medieval/early Modern usage.

Initially, it meant 'of or pertaining to baths', and over time it has retained that core meaning, remaining a specialized adjective for bath-related matters.