Historical Meaning (OED)
The word terrorism emerged from the French Revolution. In the 1790s, terrorisme referred primarily to the systematic use of terror by the revolutionary government against perceived enemies—the period known as the Reign of Terror (1793–94).
The word entered English with the sense of government by intimidation or terror. Thus, its earliest important political meaning was state-directed coercion.
During the 19th century, the meaning shifted. Russian revolutionary and anarchist movements adopted political violence, assassination and bombing as instruments intended to frighten governments and populations. “Propaganda by the deed” treated spectacular violence as a message designed to demonstrate governmental vulnerability and provoke political change.