The word mason means a construction worker who works with stone. He is also called a "stonemason". Freemasonry grew from the groups (guilds) of stonemasons in the Middle Ages. These men were building cathedrals and other big buildings. They were called freemasons because they were free, they were not servants who belonged to a rich lord, like many workers were in those days. They often changed jobs and moved from one town to another. In this way they were different from other craftsmen who often worked in one place and had guilds in one town. The stonemasons tried to keep their skills secret so only they knew how to do their job. This is probably why the Freemasons have hand shakes and passwords that they swear to keep secret.