The municipality owes its name to a Saint Welsh emigrated to Armorica: Saint Tutwall. The latter surnamed Pabu, that is to say "father," inspired a legend making him an imaginary pope known as Leon le Breton. Imaginary also or real the arrival of King Morvan in Saint-Tugdual? We are right to think that this is a reality. He was said to have stayed at Kerminisy, whose name means "place of asylum". In the middle of the countryside watered by several streams flowing into the Aër before it reaches the Ellé, stands a small jewel of architecture: the chapel Saint-Guen. It is also the starting point of a circuit of excursion full of charm. In the village, the church houses a fine example of contemporary art: "The washing of the feet", monumental fresco realized by the artist Yannig Guillevic in 2006. One does not remain indifferent to the power released by this work.