In the Middle Ages All Saints and All Souls were kept apart. Later traditions like souling and the distribution of soul cakes helped to fuse the feasts
The feast for all Saints has very early roots. Very early on after 313 when the church was legalised a common commemoration of the martyrs and saints was instituted. At that time it was celebrated on the first Sunday after Pentecost. Both St. Ephrem (d. 373) and St. John Chrysostom (d. 407) attest to this feast day in their sermons. At that time it seemed appropriate. Many of the early martyrs had died together; further there were not enough days to go around. Some time in the 8th century the celebration was moved to the autumn. Thus Bede (d. 735) recorded the celebration of all Saints on the 1st of November in England. A hundred years later Pope Gregory IV appointed the this day as All Saints Day and asked Louis the Pious to proclaim this throughout the Carolingian Empire. Not until the beginning of the new millennium the 1st of November was formally established.
The feast of All Souls developed alongside All Saints as a day for commemorating all the dead (and nut just the saints and martyrs).However, it was not until the abbot Odilio of Cluny in 998 decreed for all the Cluniac monasteries that special prayers should be offered for all the souls in purgatory, that this feast began to be accepted widely.
In the later Middle Ages these two church feasts often mingled to the consternation of theologians. Further they were coupled with more popular beliefs and traditions…
Read about the traditions of Souling and medieval Soul Cakes and get the recipes for a proper – and less tacky – medieval celebration than Halloween at