Sycophant
Sycophant was a term used in legal system of Classic Athens but in modern English it refers to someone practicing sycophancy i.e. obedient flattery.
The word sycophant has its origin in the legal system of Classical Athens. Having no police force and only a limited number of officially appointed public prosecutors, most legal cases of the time were brought by private litigants. By the fifth century BC, however, this practice had given rise to abuse by litigants who brought unjustified prosecutions. Such a litigant was called a "sycophant". The word retains the meaning of "an informer" in Modern Greek and French; but in modern English, the meaning of the word has shifted to that of an "insincere flatterer", see sycophancy.