Jacob Emden, also known as Ya'avetz (June 4, 1697 – April 19, 1776), was a leading German rabbi and talmudist who championed Orthodox Judaism in the face of the growing influence of the Sabbatean movement. He was acclaimed in all circles for his extensive knowledge.Emden was the son of the hakham Tzvi Ashkenazi, and a descendant of Elijah Ba'al Shem of Chełm. He lived most his life in Altona (now a part of Hamburg, Germany), His son was Meshullam Solomon, rabbi of the Hambro Synagogue in London who claimed authority as Chief Rabbi of the United Kingdom from 1765 to 1780.The acronym Ya'avetz (יעב"ץ, also written Yaavetz) stands for the words Yaakov (Emden) ben Tzvi (his father's name, יעקב (עמדין) בן צבי).Seven of his 31 works were published posthumously. Source: Wikipedia (en)