User blog comment:Wachotenefaso/Why don't Winchester ask angels about the Mother of All?/@comment-3481504-20120428021817/@comment-3045936-20120428032520

Salute to Supernatural convention in Vancouver, stated that Eve's original name was Occulta which is the Latin word for hidden. As she was hidden from the world as the mother of all monster with souls and hidden from Heaven and Hell eyes. As she ruled or lived in Purgatory. Hence in Mother Dearest why Cas said she is hidden from all angels. So maybe, she was maybe she wasn't known by the angel minus the Archangels or had very little info on it. As said by Castiel to Crowley no one ever found Purgatory. Hence he at least knows of that world.