austere adj.

Middle English sere, "dried up, withered, barren" (of plants, etc.), from Old English sear, from Proto-Germanic *sauzas (source also of Middle Low German sor, Dutch zoor "dry"), from PIE root *saus- "dry" (source also of Sanskrit susyati "dries, withers;" Old Persian uška- "dry" (adj.), "land" (n.); Avestan huška- "dry;" Greek auos "dry," auein "to dry;" Latin sudus "dry"). Related to sear. Figurative use from 1530s. Sere month was an old name for "August."

mid-14c., "sternness, harshness," from Old French austerite "harshness, cruelty" (14c.) and directly from Late Latin austeritatem (nominative austeritas), from austerus "severe, rigid," a figurative use, in classical Latin "harsh, sour" (see austere).

From 1580s as "severe self-discipline, ascetic practices;" hence "severe simplicity, absence of adornment or luxuries," applied during World War II to national policies limiting non-essentials as a wartime economy.

[Austerity] stands just at the edge of that frame of mind which regards self-denial as good for its own sake ; it pushes simplicity of living and the refusal of pleasure beyond what is deemed necessary or helpful to right living by the great mass of those who are equally earnest with the austere in trying to live rightly. [Century Dictionary]