Paul C. Bauschatz in 1976 suggested that the term reflects a pagan ritual which had a “great religious significance in the culture of the early Germanic people”.
The ritual according to Bauschatz was always conducted indoors, usually in a chieftain’s mead hall. Symbel involved a formulaic ritual which was more solemn and serious than mere drinking or celebration. The primary elements of symbel are drinking ale or mead from a drinking horn, speech making (which often included formulaic boasting and oaths), and gift giving. Eating and feasting were specifically excluded from symbel, and no alcohol was set aside for the gods or other deities in the form of a sacrifice.
Bauschatz’ lead is followed only sporadically in modern scholarship.
Source: Symbel – Wikipedia