Gist

According to the Old English Dictionary:

gyst, es;

GIST

m. YEAST, barm, froth; spuma cerevisiæ, Herb. 21, 6; Lchdm. i. 118, 10. Niwue gist new yeast, L. M. ii. 51, 1; Lchdm. ii. 266, 1. [Prompt. Parv. ȝeest spuma.] gist,gist-