Orininally a member of an Indian sect ("thuggee") that worshipped Kali and killed people to rob them. Famous for strangulating people. One cult head was tried for more than 900 murders.
The word has later evolved to mean "robber, murderer" in general.
The earliest thuggee account was R. C. Sherwood's Of the Murderers Called Phansigars which was based on interrogations and depositions of thuggees and published in 1820