The word nefarious has its origin in Latin. It was taken from the word nefārius. This was obtained from nefās which means crime or transgression. The word nefās is formed of two parts: ne and fās. The first part 'ne' means 'not' and the second part 'fās' means divine law. Nefarious is an adjective. Someone or something that is nefarious is known as an extremely wicked person or thing. The quality possessed by such an individual is termed as nefariousness. For example: a nefarious plot. It is nasty plot.