The Amagüestu (magosto, magüestu, magostu, castañada or amagostu) is a traditional festival thast takes place in the Iberian Peninsula related to the annual recollection of chestnuts and the ending of summer.
"Etymological origins are unknown, but there are several theories for the Magosto name: Magnus Ustus (great fire) or Magum Ustum (highlighting the magical character of fire).
It is a festival with Celtic roots that celebrates the end of summer and the beginning of winter. In all the regions where it is celebrated, and especially in Galicia, it is deeply related to the cult of the dead. It is customary to leave the fire of the house lit and place food around the fireplace to welcome back the spirits of deceased members of the family". Wikipedia