[the OlLine Rebel]

I doubt “terrorist” was in the vocabulary.

[BroJoeK]

the OlLine Rebel: "I doubt “terrorist” was in the vocabulary."

That's an interesting point, I might even agree.
What I know for certain is:

1. The words "terrorism" or "terrorist" were coined during the French Revolution referring to Robespierre's Reign of Terror, circa 1793.

2. Those words were soon used (1795) by men like Thomas Jefferson, John Adams and James Madison to describe events in France.

3. By 1813 Adams also used "terrorism" (writing to Jefferson) in reference to events in the USA such as Shays Rebellion, the Whiskey Rebellion & Fries Rebellion.

4. "Terrorism" first appeared in Webster's dictionary in 1840, with a very generalized definition, but "terrorist" did not appear until 1864 and it then referred specifically to the French government's revolutionary tribunal in 1793.

All of this seems to confirm your suggestion that while those words were coined long before the Civil War, they were not commonly used as we use them until long after.

Good point.

[x]

The word “terrorist” was around and was used by Jefferson, Madison, and Adams, but it primarily referred to state violence on the model of the French Revolution. The word was evolving and might possibly have been used in different ways in the Civil War era, but it was the late 19th century Russian revolutionaries and anarchist assassins who laid the template for the modern idea of terrorism. According to Google ngrams the word “abolitionist” was many, many, many times more common than the word “terrorist” in the 19th century.