Final answer:
Karl Marx originated the term lumpenproletariat to characterize marginalized sectors of the society like the homeless. This term was part of his broader analysis of class struggle and the economic inequalities under capitalism.
Step-by-step explanation:
The theorist who coined the term lumpenproletariat to describe those 'discarded' by the system, such as the homeless, was Karl Marx. Marx's analysis of society was centered on the economic struggles and the class divisions between the bourgeoisie and the proletariat. The term lumpenproletariat refers to a layer of the working class that is so impoverished and devoid of class consciousness that they are effectively marginalized from the class struggle. Marx believed that this group, unlike the proletariat, did not have a clear sense of collective interest and, as such, could not be relied upon to contribute to the overthrow of the capitalist system, which he opined would eventually be replaced by socialism.