From Greek 'austēros' (making the tongue dry) — originally a wine-tasting term for tannic puckering, extended to severity of character.
Severe or strict in manner or attitude; having no comforts or luxuries; simple and unornamented.
From Old French austere (stern, severe), from Latin austērus (harsh, tart, sour), from Greek austēros (harsh, rough, bitter, making the tongue dry), from auein (to dry), possibly from PIE *h₂sews- (dry). The Proto-Indo-European root conveyed physical dryness, and Greek preserved this concretely: austēros first described the astringent taste of unripe fruit or rough wine that dries the mouth. The metaphorical extension from physical dryness to moral severity — a dry, unadorned character — was already complete in Greek, where austēros described both harsh flavours and stern personalities. Latin borrowed the word with both senses
The word began as a wine-tasting term: Greek 'austēros' described wine that dried out the mouth — what modern sommeliers call 'tannic.' The leap from unripe-grape dryness to severe simplicity is a metaphor that wine-drinking cultures found entirely natural: both austerity and tannin strip away softness.