'polydipsic' originates from Greek, specifically the elements 'poly' and 'dipsa', where 'poly' meant 'many' and 'dipsa' meant 'thirst'.

'polydipsic' changed from New Latin/Neo-Latin forms such as 'polydipsia' and Late Latin 'polydipsicus' and eventually became the modern English adjective 'polydipsic'.

Initially, it conveyed the idea 'many thirsts' (or being characterized by thirst); over time it evolved into its current medical meaning of 'having excessive thirst'.