Meaning

noun minimal (or marginal) resources for subsisting

noun a means of surviving

noun the state of existing in reality; having substance

originFrom Middle English subsistence; partly from Middle French subsistence (modern French subsistance) and partly from its etymon Late Latin subsistentia (“substance, reality, in Medieval Latin also stability”), from Latin subsistēns, present participle of subsistere (“to continue, subsist”). Perhaps also partly from subsist + -ence.

Etymology from Wiktionary, CC BY-SA 3.0