Meaning

noun a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey

noun any of various single-celled fungi that reproduce asexually by budding or division

originFrom 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”).

Etymology from Wiktionary, CC BY-SA 3.0