What is "tippen"

Tippen, also known as Dreiblatt or Zwicken, is a historical German 3-card plain-trick game and was a popular gambling game for three or more players. In Denmark essentially the same game was known as Trekort.

The game was described in 19th century anthologies and encyclopedias but appears related to Loo, which was already described in the 18th century. In some locations the game was illegal.