In the olden days it was the place where the two roads leading to the Lys Valley met, on the right and left bank of the river of the same name. Guillemore and its ravine established the borders between the “Mandement de Vallaise” and the “Mandement di Issime and Gressoney”. The name of Guillemore has several variations: Guymour - Guimor - Guymor - Gueymor.
Considering the fact that it is a strategic place and highly significant from a morphological point of view, it is believed that a part of the toponym is fairly old.