What is the X in X-mas?
1810, "member of a gang of murderers and robbers in India who strangled their victims," from Marathi thag, thak "cheat, swindler," Hindi thag, perhaps from Sanskrit sthaga-s "cunning, fraudulent," possibly from sthagayati "(he) covers, conceals," from PIE root *(s)teg- "cover" (see stegosaurus). Transferred sense of "ruffian, cutthroat" first recorded 1839. The more correct Indian name is phanseegur, and the activity was described in English as far back as c.1665. Rigorously prosecuted by the British from 1831, they were driven from existence, but the process extended over the rest of the 19c.