アイルランド神話では、'''カー・イボルメース'''(Caer Ibormeith)はコナハトのシド・ウアムイン(Sid Uamuin)の王子エサール・アヌブアイル(Ethal Anbuail)の娘である。Anbuail)の娘である。1年以上続いた[[オェングス]]の夢の中で、カー・イボルメースがベッドの横に立っていたが、[[オェングス]]が手を伸ばすと彼女は消えてしまうのだった<ref>https://aliisaacstoryteller.com/2015/10/06/the-aisling-not-so-sweet-dreams-in-irish-mythology/, The Aisling Not so Sweet Dreams in Irish Mythology, 2015-10-06, aliisaacstoryteller, 2017-12-09</ref>。
In [[Irish mythology]], '''Caer Ibormeith''' was the daughter of Prince [[Ethal|Ethal Anbuail]] of [[Sid Uamuin]] in [[Connacht]]. In [[Óengus]]’s dream, which lasted over a year, Caer Ibormeith stood beside his bed though when he reached out for her, she would disappear.<ref>{{Cite news|url=https://aliisaacstoryteller.com/2015/10/06/the-aisling-not-so-sweet-dreams-in-irish-mythology/|title=The Aisling {{!}} Not so Sweet Dreams in Irish Mythology|date=2015-10-06|work=aliisaacstoryteller|access-date=2017-12-09|language=en-GB}}</ref> Every alternate [[Samhain]] she would turn to human form for one day, which begins at sunset, and after that, she would revert into being a [[swan]], in which form she would remain for a year before becoming human again the following Samhain.
[[Óengus]] went in search for this girl in his dreams at the [[lake of the Dragon's Mouth]] and found 150 girls chained in pairs, his girl Caer Ibormeith, among them. Óengus was told he could marry Caer if he could identify her in her swan form. He chose correctly and with that Óengus turned himself into a swan and they flew away together, to the [[Brú na Bóinne]]/palace on the River Boyne near [[Slane]], which was his long standing place of residence. The pair sang beautiful music as they went, that put all listeners throughout Ireland asleep for three days and nights.<ref name=MJ-Oengus>[http://www.maryjones.us/ctexts/oengus.html The Dream of Oengus] {{Webarchive|url=https://web.archive.org/web/20131124041701/http://www.maryjones.us/ctexts/oengus.html# |date=2013-11-24 }} The Celtic Literature Collective</ref> Caer would marry with [[Óengus]] of the [[Tuatha de Dannan]], and, amongst other things, become foster-mother of [[Diarmuid]].