A pogrom is a violent massacre or persecution of an ethnic or religious group, particularly one aimed at Jews. The term, a Yiddish variation on a Russian word meaning "thunder", originally entered the English language to describe 19th and 20th-century attacks on Jews in the Russian Empire; similar attacks against Jews at other times and places also became retrospectively known as pogroms. The word is now also sometimes used to describe publicly sanctioned purgative attacks against non-Jewish ethnic or religious groups. Significant pogroms in the Russian Empire included the Odessa pogroms, Warsaw pogrom (1881), Kishinev pogrom (1903), Kiev Pogrom (1905), and Białystok pogrom (1906), and, after the 1917 Russian Revolution, the Lwów pogrom (1918) and Kiev Pogroms (1919). The most significant pogrom in Nazi Germany was the Kristallnacht of 1938 in which at least an initial 91 Jews were killed by Nazi soldiers, a further 30,000 were arrested and subsequently incarcerated in concentration camps (many of which eventually died there), more than 1,000 synagogues burned, and over 7,000 Jewish businesses destroyed or damaged. Such purges have not been limited to Central Europe, however: notorious pogroms of World War II included the 1941 Farhud in Iraq, the July 1941 Iaşi pogrom in Romania – in which over 13,200 Jews were killed – as well as the Jedwabne pogrom in Poland. Post World War II pogroms included the 1945 Tripoli pogrom, the 1946 Kielce pogrom and the 1947 Aleppo pogrom. Pogroms against non-Jews include the 1966 anti-Igbo pogrom against Igbos in southern Nigeria, the 1955 Istanbul Pogrom against Greeks, the 1920 Shusha pogrom, the 1988 Sumgait pogrom, the Kirovabad pogrom, in which ethnic Armenians were targeted and the 2008 anti-Immigrant pogrom in South Africa in which African immigrants were targeted.