The article discusses the history of two terms closely related to the notion of court service in the Middle ages: courtois and courtisan. At first glance, the words do not have a common etymon, although belong to the same semantic family. It gives an interesting occasion for a comparative research. Basing upon several French writings of the XII–XV centuries the author analyzes the peculiarities of usage of both the terms which ended by the full replacement the word “courtois” to the end of the Middle ages.