 In Rheinische Dokumenta, it marks vowels that are more open than those denoted by their base letters Ää, Oo, Öö.In two cases, it can be combined with umlaut marks.The "E caudata" ("ę"), a symbol similar to an "e" with ogonek, evolved from a ligature of "a" and "e" in medieval scripts, in Latin and Irish palaeography.