Ressentiment was first introduced as a philosophical/psychological term by the 19th century philosopher Søren Kierkegaard. Friedrich Nietzsche later independently expanded the concept; Walter Kaufmann ascribes Nietzsche's use of the term in part to the absence of a proper equivalent term in the German language, contending that said absence alone "would be sufficient excuse for Nietzsche," if not for a translator. The term came to form a key part of his ideas concerning the psychology of the 'master–slave' question (articulated in Beyond Good and Evil), and the resultant birth of morality. Nietzsche's first use and chief development of ressentiment came in his book On The Genealogy of Morals; see esp §§ 10–11).http://www.bu.edu/wcp/Papers/Anth/AnthMore.htmhttp://www.nietzschecircle.com/essayArchive1.html. Ressentiment was translated as envy in Hong's translation of Kierkegaard's .
The term was also put to good use by Max Scheler in his book Ressentiment, published in 1912, and later suppressed by the Nazis.
Currently of great import as a term widely used in psychology and existentialism, ressentiment is viewed as an influential force for the creation of identities, moral frameworks and value systems. However there is debate as to what validity these resultant value systems have, and to what extent they are maladaptive and destructive.