yester- Look up yester- at Dictionary.com
Old English geostran "yesterday," from Proto-Germanic *gester- (cognates: Old High German gestaron, German gestern "yesterday," Old Norse gær "tomorrow, yesterday," Gothic gistradagis "tomorrow"), originally "the other day" (reckoned from "today," either backward or forward), from PIE root *dhgh(y)es- "yesterday" (cognates: Sanskrit hyah, Avestan zyo, Persian di, Greek khthes, Latin heri, Old Irish indhe, Welsh doe "yesterday;" Latin hesternus "of yesterday").