That Raphael Lemkin, a Polish Jew who lost 72 of the 74 members of his family in the Holocaust, coined the term "genocide" in 1944 to describe the Nazis' systematic annihilation of the Jews of Europe. A portmaneau of the Greek genos - family; tribe, race, and Latin caedere - to kill; to cut down, Lemkin's specifc definiton was "the destruction of a nation or an ethnic group."
Lemkin, a lawyer and scholar, escaped Warsaw when the Germans invaded Poland. He eventually immigrated to the United States, where he became the driving force behind the drafting and adoption of the International Convention on the Prevention and Punishment of the Crime of Genocide, adopted unanimously by the United Nations General Assembly in Paris on December 9, 1948. The Convention was brought into force in 1950, when the required number of countries had ratified its provisions.
Ironically, the United States, which took a leading role in the creation of the Convention, was one of the last countries to ratify it. Not until 1988, forty years after its adoption, did the U.S. Senate give its advice and consent to the Genocide Convention.
For more information about Lemkin and the Genocide Convention, see:
Lawrence J. LeBlanc, The United States and the Genocide Convention, Duke University Press, 1991.
Raphael Lemkin, Axis Rule in Occupied Europe, Columbia University Press, 1944