The surname Fivaz, sometimes written Fiwaz or F-i-v-v-a-z, is found at Payerne, in the canton of Vaud, toward the beginning of the 16th Century. A letter granting nobility to the brothers Michel, Jean, and Claude, all sons of Claude Fivaz son of Pierre, still survives, and on the basis of this you will sometimes find the name listed as "de Fivaz". One branch, that of the younger Claude, remained Catholic and settled in Fribourg. The other branch, evidently from Michel, became Protestant and remained in Payerne (a later branch took citizenship at Corcelles-près-Payerne when Corcelles was split off from Payerne). But, other apparently unrelated Fivaz families are found in the same vicinity, for example at Sassel.
Because there were multiple families with the same surname, it may be difficult to establish which one you descend from, and it is not necessarily true that Fivaz or similar names are always from Switzerland!