the word 'surtax' is a transparent compound formed in english from french and latin elements. the prefix 'sur-', derived from the latin preposition 'super', carries the meaning of 'over' or 'above'. it is attached to the noun 'tax', which originates from the latin verb 'taxare', meaning to assess or charge. the literal construction 'over-tax' logically evolved into the modern, specific fiscal term denoting an extra or additional levy imposed on top of an existing tax, clearly conveying the concept of a charge layered upon another.

Structure: sur (over) + tax (a compulsory contribution to state revenue) sur- (from old french, ultimately from latin 'super', meaning 'over, above'); tax (from latin 'taxare', meaning 'to appraise, charge, censure').