Source : Webster's Revised Unabridged Dictionary (1913)

Proletary \Prol"e*ta*ry\, n.; pl. {Proletaries}. [ L.
   proletarius, fr. proles offspring. Cf. {Prol['e]taire}.]
   (Rom. Antiq.)
   A citizen of the lowest class, who served the state, not with
   property, but only by having children; hence, a common
   person.