"Log" is used to describe a detailed record (particularly of travel or shipping) because in the age of sail, information about a ship's speed was gleaned by throwing an actual log out a porthole with knots tied at regular intervals, and the info was record in the log book.
In ancient Rome, salt was used to preserve food, making it a valuable resource. So valuable salt was often used as wages for soldiers - called Salarium. Salarium turned into the French word Salaire, and later, Salary in English. Go be brillant at diner tonight.