'hydrodynamic-finned' is a compound formed from the adjective 'hydrodynamic' and the past-participle-derived adjective 'finned'. 'hydrodynamic' derives from Greek elements 'hydro-' (from Greek 'hudōr') meaning 'water' and 'dynamic' (from Greek 'dunamikos') meaning 'power' or 'force'; 'finned' derives from the noun 'fin' (Old English 'finn') referring to a projecting limb used for steering or propulsion.

'hydrodynamic' entered English usage as a scientific adjective in the 19th century from modern coinage of Greek roots and technical Latin/English usage; 'fin' existed in Germanic languages (Old English 'finn') and developed into the modern English noun 'fin', with the adjectival/past-participle form 'finned' used to describe objects bearing fins. The compound 'hydrodynamic-finned' is a descriptive technical formation combining these elements.

Initially, the components separately meant 'water' + 'force/power' (for 'hydrodynamic') and a projecting limb for movement (for 'fin'); over time the compound came to denote specifically that an object is equipped with fins shaped or arranged to optimize movement through water.