As can be seen, the figure of Fionn’s window has 5 circles. In my opinion we can find the meaning of the layers in the tale about Kilhwch and Olwen or the Twrch Trwyth from: The Mabinogion. In this story Arthur and his warband set out for the rescue of Mabon ap Modron. Roughly translated Mabon ap Modron translate into the good son of the madres (the three godesses are a common theme in Western European mythology)
The tale about the rescue goes along like this:
They went forward until they came to the Ousel of Cilgwri. And Gwrhyr adjured her for the sake of Heaven, saying, “Tell me if thou knowest aught of Mabon the son of Modron, who was taken when three nights old from between his mother and the wall.” And the Ousel answered, “When I first came here, there was a smith’s anvil in this place, and I was then a young bird; and from that time no work has been done upon it, save the pecking of my beak every evening, and now there is not so much as the size of a nut remaining thereof; yet the vengeance of Heaven be upon me, if during all that time I have ever heard of the man for whom you inquire. Nevertheless I will do that which is right, and that which it is fitting that I should do for an embassy from Arthur. There is a race of animals who were formed before me, and I will be your guide to them.”
So they proceeded to the place where was the Stag of Redynvre. “Stag of Redynvre, behold we are come to thee, an embassy from Arthur, for we have not heard of any animal older than thou. Say, knowest thou aught of Mabon the son of Modron, who was taken from his mother when three nights old?” The Stag said, “When I first came hither, there was a plain all around me, without any trees save one oak sapling, which grew up to be an oak with an hundred branches. And that oak has since perished, so that now nothing remains of it but the withered stump; and from that day to this I have been here, yet have I never heard of the man for whom you inquire. Nevertheless, being an embassy from Arthur, I will be your guide to the place where there is an animal which was formed before I was.”
So they proceeded to the place where was the Owl of Cwm Cawlwyd. “Owl of Cwm Cawlwyd, here is an embassy from Arthur; knowest thou aught of Mabon the son of Modron, who was taken after three nights from his mother?” “If I knew I would tell you. When first I came hither, the wide valley you see was a wooded glen. And a race of men came and rooted it up. And there grew there a second wood; and this wood is the third. My wings, are they not withered stumps? Yet all this time, even until to-day, I have never heard of the man for whom you inquire. Nevertheless, I will be the guide of Arthur’s embassy until you come to the place where is the oldest animal in this world, and the one that has travelled most, the Eagle of Gwern Abwy.”
Gwrhyr said, “Eagle of Gwern Abwy, we have come to thee an embassy from Arthur, to ask thee if thou knowest aught of Mabon the son of Modron, who was taken from his mother when he was three nights old.” The Eagle said, “I have been here for a great space of time, and when I first came hither there was a rock here, from the top of which I pecked at the stars every evening; and now it is not so much as a span high. From that day to this I have been here, and I have never heard of the man for whom you inquire, except once when I went in search of food as far as Llyn Llyw. And when I came there, I struck my talons into a salmon, thinking he would serve me as food for a long time. But he drew me into the deep, and I was scarcely able to escape from him. After that I went with my whole kindred to attack him, and to try to destroy him, but he sent messengers, and made peace with me; and came and besought me to take fifty fish spears out of his back. Unless he know something of him whom you seek, I cannot tell who may. However, I will guide you to the place where he is.
So they went thither; and the Eagle said, “Salmon of Llyn Llyw, I have come to thee with an embassy from Arthur, to ask thee if thou knowest aught concerning Mabon the son of Modron, who was taken away at three nights old from his mother.” “As much as I know I will tell thee. With every tide I go along the river upwards, until I come near to the walls of Gloucester, and there have I found such wrong as I never found elsewhere; and to the end that ye may give credence thereto, let one of you go thither upon each of my two shoulders.” So Kai and Gwrhyr Gwalstawd Ieithoedd went upon the two shoulders of the salmon, and they proceeded until they came unto the wall of the prison, and they heard a great wailing and lamenting from the dungeon. Said Gwrhyr, “Who is it that laments in this house of stone?” “Alas, there is reason enough for whoever is here to lament. It is Mabon the son of Modron who is here imprisoned; and no imprisonment was ever so grievous as mine, neither that of Lludd Llaw Ereint, nor that of Greid the son of Eri.” “Hast thou hope of being released for gold or for silver, or for any gifts of wealth, or through battle and fighting?” “By fighting will whatever I may gain be obtained.”
Then they went thence, and returned to Arthur, and they told him where Mabon the son of Modron was imprisoned. And Arthur summoned the warriors of the Island, and they journeyed as far as Gloucester, to the place where Mabon was in prison. Kai and Bedwyr went upon the shoulders of the fish, whilst the warriors of Arthur attacked the castle. And Kai broke through the wall into the dungeon, and brought away the prisoner upon his back, whilst the fight was going on between the warriors. And Arthur returned home, and Mabon with him at liberty.
So in order to save Mabon Arthur has to visit the oldest creatures in the land, all also have a strong connection with the otherworld. In order they visit:
- Ousel of Cilgwri
- Stag of Redynvre
- Owl of Cwm Cawlwyd
- Eagle of Gwern Abwy
- Salmon of Llyn Llyw
Some connect the myth of the 3 birds living in the world tree with Ousels. The salmon has many myths, and is filled with knowledge on the world. So from the outside, we find singing birds who connect to man kind and on the inside there is divine knowledge. The myth of Fionn, also contains such a salmon, of which can be found more on the page dealing with Fionn.