yester- Look up yester- at Dictionary.com
Old English geostran "yesterday," from Proto-Germanic *gester- (source also of 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" (source also of Sanskrit hyah, Avestan zyo, Persian di, Greek khthes, Latin heri, Old Irish indhe, Welsh doe "yesterday;" Latin hesternus "of yesterday").