Where did the word scot originate?
It is slang for "Scottish," which comes from "Scotland," which is a country.
A scot is a Scandinavian word for tax or payment. It came to the UK as redistributive taxation, levied in the early 13th century, as a form of municipal poor relief. The term is a contraction of 'scot and lot'. Scot was the tax and lot, or allotment, was the share given to the poor. Being scot free just meant that you didn't have to pay the tax.