'balmy' originates from English, specifically the word 'balm' plus the suffix '-y', where 'balm' ultimately comes from Latin 'balsamum' and Greek 'balsamon'.

'balsamum' (Latin) and 'balsamon' (Greek) passed into Old French and Middle English as 'balm' (or 'balme'), and the adjective form 'balmy' developed in early modern English (mid-16th century), eventually yielding the modern English 'balmy' and its forms like 'balmiest'.

Initially it referred to the aromatic ointment 'balm' (an aromatic, soothing substance); over time the meaning extended metaphorically to describe soothing, mild, or pleasantly warm conditions, and now 'balmy' (and 'balmiest') commonly mean 'mild and pleasant' (especially of weather).