Drinking “Brüderschaft” (brotherhood drinking) is a widespread drinking custom in many countries indicating switching to a personal form of address by means of drinking. This custom is to link arms holding the glass reaching through the crook of the arm of the other person. It is followed by a kiss afterwards. Then you introduce yourself with your first name, and form a kind of “brotherhood”.
The origin of the ritual “Brüderschaft” drinking cannot be precisely determined but it was already mentioned in the late Middle Ages. Some believe it dates back to magical rites: Rites such as mutual drinking of blood or joint dipping of hands in animal blood committed the participants to the same goals and ideals and thus formed a brotherhood.
The custom of drinking “Brüderschaft” was also mentioned in the Jus Potandi ,or Zechrecht a legal-parodic text published in 1616 by an anonymous German author.