They are names of local saints, but normally they are only used in the parishes where there's a chapel dedicated to that saint, ie. you'll find men called Tugdual mainly in parishes where there are chapels dedicated to Saint Tugdual.
so in my area: Tugdual, Méven, Ouen, Gildas, Guénolé, Goulven, Armel, Maudé, Guénaël, Ildut...
(in Breton: Tudal, Mevenn, Aoden, Gweltaz, Gwenole, Goulven, Armael, Maodez, Gwenael, Ildud)
but there are loads throughout Brittany... many aren't even recognized by the Catholic church. As in Ireland, there are saints who were pagan gods or heroes, who have been christianised by adding "saint-" before them, or saints like "zant Diboen" (saint Withoutpain, whose fountain eases pains) or "Zant Minerh" (from mil nerzh, 1000 strengths)...
