1894, from German Zweiback "biscuit," literally "twice-baked," from zwei "two, twice" + backen "to bake;" loan-translation of Italian biscotto (see biscuit).
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biscuit n.
"kind of hard, dry bread baked in thin flat cakes," respelled early 19c. from bisket (16c.), ultimately (besquite, early 14c.) from Old French bescuit "biscuit" (12c.), altered under influence of cognate Old Italian biscotto, both from Medieval Latin biscoctum, literally "twice-baked," from Latin (panis) bis coctus "(bread) twice-baked;" see bis- + cook (v.). The U.S. sense of "small, round soft bun" is recorded from 1818.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dvau, Avestan dva, Greek duo, Latin duo, Old Welsh dou, Lithuanian dvi, Old Church Slavonic duva, Old English twa, twegen, German zwei, Gothic twai "two;" first element in Hittite ta-ugash "two years old."