Proletariat descends from Latin prōlētārius, the lowest class of Roman citizen whose only service to the state was producing children (prōlēs, 'offspring'). The word's root reaches back to PIE *h₂el- (to grow, nourish), the same ancient root that gives us adolescent, adult, alumnus, and aliment. Revived in 1830s France by socialist thinkers and immortalised by Marx and Engels, this devastating Roman legal insult became the defining term of modern class politics.
The class of wage-earners in a capitalist society whose only significant economic asset is their labour; historically, in Roman law, the lowest class of citizens who served the state solely through the production of offspring.
From French prolétariat, itself derived from Latin prōlētārius, a legal term in the Servian constitution (attributed to Servius Tullius, 6th c. BCE) designating the lowest census class of Roman citizens — those too poor to contribute taxes or military service, whose sole contribution to the res publica was the production of offspring (prōlēs). The Latin term is recorded by Aulus Gellius (Noctes Atticae XVI.10, 2nd c. CE): 'proletarii dicti sunt, qui in civitate nihil praeter prolem haberent' — 'those were called proletarii who possessed nothing in the state
The Roman state's classification was breathtakingly blunt: if you were too poor to contribute money or military service, your civic worth was reduced to your reproductive capacity — you were literally a 'child-maker' for the republic. Two millennia later, Marx seized this ancient insult and forged it into a revolutionary identity, transforming a label of civic contempt into a badge of world-historical agency.