The town is one of the best known in the archipelago of the Azores as it hosts the pilgrimage of Senhora dos Milagres, held annually on the second Sunday in September. The toponym Serreta, common in the Azorean toponymia in the form of serreta or serretinha as diminutive of saw, has its origin in the abundance of hills in that region of the island Terceira, forming an extension until the sea of the Mountain range of Santa Bárbara.
Source: wikipedia.org