TYRNAU, ISAAC (end of 14th century), Austrian rabbi and compiler of a book of *minhagim. Tyrnau's teachers were Abraham *Klausner, Sar Shalom of Neustadt, and *Aaron Neustadt. Until recently it was assumed that his name derived from Trnava (Tyrnau) in Hungary (now Slovakia), but modern scholars incline more to the view that he came from Austria. He was born in Vienna and apparently subsequently moved to Tyrnau in Austria, from where it is possible that he went to minister as rabbi of Pressburg although some scholars deny that he was ever in Pressburg. Little is known about his life except that in 1420 he contacted Jacob *Moellin regarding a divorce.
Tyrnau's fame rests upon his book of minhagim. Basing himself largely on his teacher, Klausner, he set down customs and codes of conduct for the whole year, and they were subsequently adopted in most communities in Austria, Hungary, and Styria. As Tyrnau wrote in the preface, his aim was to create a common minhag. As a result of the *Black Death (1348–50), which had uprooted most of the communities of Germany, "scholars became so few.… I saw localities where there were no more than two or three persons with a real knowledge of local custom." His description is concise and his style easy. The book enjoyed great popularity among German and Polish Jewry. Glosses by a Hungarian scholar, whose identity is not certain, apparently were added to the book and published together with it. The first edition was printed in Venice (1566) and has been frequently republished often as an appendix to the prayer book. Similarly a German translation by Simon Guenzburg (Mantua, 1590) has often been reprinted. A legend has been preserved to the effect that the Hungarian crown prince fell in love with the beautiful daughter of Tyrnau, and out of love for her renounced the throne, became converted to Judaism, and went to study Torah from Sephardi rabbis. On his return to Hungary he entered into a clandestine marriage with her and continued to study under his father-in-law. His identity was accidentally discovered by Catholic priests who demanded that he revert to his original faith. When he refused, he was burned at the stake and the Jews expelled from Tyrnau (Eẓba Elohim, o Ma'aseh Ray she-Eira le-ha-Rav Yiẓḥak Tyrnau; "The Finger of God, or What Happened to R. Isaac Tyrnau," the author of Sefer ha-Minhagim, 1857).
Michael, Or, no. 328; J.J. Cohen in: Ha-Ma'yan, 8 (1968), no. 4, 4–12; Weingarten, ibid., 10 (1970), no. 2, 48–56.