There is a legend about three brothers - Lech, Czech and Rus. They all wanted to form a new country. One day, in the evening, Lech saw the white eagle at the background of red sky (white eagle on the red background is polish national symbol), and he decided to place a new town there. He named it Gniezdno (now it's called Gniezno, because previous version was hard to pronaunce). That was the first capital city of Poland.
There are also stories about two other brothers - after all, Rus form Rosja (Russia) and Czech made Czechy.