yea (adv.)

Old English geon "that (over there)," from Proto-Germanic *jaino- (source also of Old Frisian jen, Old Norse enn, Old High German ener, Middle Dutch ghens, German jener, Gothic jains "that, you"), from PIE pronominal stem *i- (source also of Sanskrit ena-, third person pronoun, anena "that;" Latin idem "the same," id "it, that one;" Old Church Slavonic onu "he;" Lithuanian ans "he"). As an adverb from late 15c., a shortening of yonder.

word of assent to a question, 1570s, of unknown origin; perhaps a variant of I, meaning "I assent;" or an alteration of Middle English yai "yes" (see yea); or from aye (adv.) "always, ever."

Old English gise, gese "so be it!," probably from gea, ge "so" (see yea) + si "be it!," from Proto-Germanic *sijai-, from PIE *si-, optative stem of root *es- "to be." Originally stronger than simple yea. Used in Shakespeare mainly as an answer to negative questions. As a noun from 1712. Yes-man is first recorded 1912, American English.