'bigwig' originates from English, specifically a compound of 'big' and 'wig', where 'big' meant 'large' and 'wig' referred to a hairpiece (worn as a social or professional status symbol).

'bigwig' appeared in the 18th century as slang referring to men who wore large (often powdered) wigs; it soon was used figuratively to mean an important or influential person and has remained in that figurative sense.

Initially it meant 'a person who literally wore a large wig' (or referred to such a wig as a status symbol), but over time it evolved into its current figurative meaning of 'an important or influential person'.