The term lumpenproletariat (trans. 'ragged proletariat' or 'lumpen masses') was introduced in The German Ideology by Karl Marx and Friedrich Engels to describe the lowest level of the proletariat, including vagrants, homeless, the unemployed, welfare recipients, and criminals. Other socialist terms for the homeless and unemployed are shiftless elements and social parasites.
According to Marx the lumpenproletariat would have little motive for taking part in revolution and would in fact wish to maintain their class structure, as they often depended on the higher classes. Marx thought of the lumpenproletariat as a counterrevolutionary threat to the idea of Marxist revolution.
In the Communist Manifesto, Marx said, “The ‘dangerous class,’ the social scum, that passively rotting mass thrown off by the lowest layers of the old society, may, here and there, be swept into the movement by a proletarian revolution; its conditions of life, however, prepare it far more for the part of a bribed tool of reactionary intrigue.”
Peasants, on the other hand, were considered by Marx and Engels to be unqualified to be any social class because of their so-called fragmentation and ignorance.
Lumpenproletariat were often the target for arrest, detention, and forced labor in concentration camps set up by Vladimir Lenin shortly after the October Revolution in the newly created Union of Soviet Socialist Republics.