Yeast

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Old English, of Germanic origin; related to Dutch gist and German Gischt ‘froth, yeast’, from an Indo-European root shared by Greek zein ‘to boil’.

wiktionary

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From Middle English yest, yeest, gest, gist, from Old English ġist, ġyst, from Proto-West Germanic *jestu, from Proto-Germanic *jestuz. Cognate with Saterland Frisian Jääst(“yeast”), West Frisian gêst, gist(“yeast”), Dutch gist(“yeast”), German Low German Gest(“yeast”), German Gischt(“sea foam”), Swedish jäst(“yeast”), Norwegian jest(“yeast”), Icelandic jöstur(“yeast”).

etymonline

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yeast (n.)

Old English gist "yeast, froth," from Proto-Germanic *jest- (source also of Old Norse jastr, Swedish jäst, Middle High German gest, German Gischt "foam, froth," Old High German jesan, German gären "to ferment"), from PIE root *yes- "to boil, foam, froth" (source also of Sanskrit yasyati "boils, seethes," Greek zein "to boil," Welsh ias "seething, foaming").