As I was reading Old Mortality by Sir Walter Scott, I came across the following words, which sent me to the dictionaries and the encyclopedias.

Achan

A man mentioned in the Bible in the Book of Joshua in connection with the fall of Jericho and conquest of Ai. (Wikipedia)

Ci-devant

From or in an earlier time (used to indicate that someone or something once possessed a specified characteristic but no longer does so.) (Oxford Dictionaries, Wikipedia)

Erastianism

The doctrine that the state is superior to the church in ecclesiastical matters. It is named after the 16th-century Swiss physician and Zwinglian theologian Thomas Erastus, who never held such a doctrine. (Encyclopaedia Britannica)

Kailbrose

A traditional Scottish dish of creamed kale and oats (Celtnet Recipes; How Stuff Works, Visit Dunkeld) [I may have to try these kale brose recipes!]

Prelatist

A person who supported an episcopal view church government (Dictionary.com, Wikipedia, EHow)

Sybo

A spring onion (Dictionary.com)

Vidette

A mounted sentry in advance of the outposts of an army. (The Free Dictionary)