In Welsh mythology, Modron ("divine mother") was a daughter of Afallach, derived from the Gaulish goddess Matrona. She may have been the prototype of Morgan le Fay from Arthurian legend. She was the mother of Mabon, who bears her name as "Mabon ap Modron" ("Mabon, Son of Modron") and who was stolen away from her when he was three days old and later rescued by King Arthur[....]
Her Gaulish counterpart Matrona is a Celtic mother goddess and tutelary goddess of the River Marne. She is also a fertility and harvest deity often equated with Greece's Demeter or Ireland's Danu. InBritain, she appears as a washerwoman, and thus there would seem to be a connection with the Morríganand
In Celtic mythology, Dea Matrona ("divine mother goddess") was the goddess of the river Marne in Gaul.In many areas she was worshipped as a triple goddess, and known as Deae Matres (or Deae Matronae), with a wider sphere of believed[who?] influence. This triadic deity is well attested throughout northern Europe (more generally as the Matres or Matrones), not just in Celtic areas, and was similar to the Fates, Furies, Norns, and other such figures.
As for the actual Myth, it can be found in many sites. Keeping in mind that the written myth was much more recent than the oral myth (or if there were other things written about it, we can't find it), the basic theme is:
'Mabon' is named after the Welsh God Mabon, known as the Son of Light or the Divine Youth. In Welsh myth Mabon was taken from his mother Modron - the Healer, the Guardian of the Outerworld. There are variations of this myth but one of the oldest versions is that Mabon is rescued through the wisdom of ancient animals, the Stag, Eagle, Blackbird, Owl and Salmon. All along Mabon had been merely resting happily in his mothers womb, being nurtured and learning new lessons, until he is reborn stronger and wiser.So, we have a few different things going on. Another thing worth mentioning is the similarity between Rhiannon losing her child, and having him returned, much older than he should be.
Either way, I was trying to find a base, a sort of 'pre-myth' myth.
Modron gives birth, and Mabon lies between her and the wall, and then is taken for three days (or really I don't know if the three days is a for sure, or just one of many theories. The Three Day theme is pretty popular in death/rebirth myths, right down to Jesus). Regardless, The Divine Mother gives birth, the child is stolen and then reappears within her womb older and having learned new lessons, is reborn stronger and wiser.
Well, what came to me was an image of a fallen fruit from the harvest. The fruit (or seed) that has been birthed from the fruits of summer falls to the ground, to our Earth Mother. Shortly thereafter, the seed is drawn down into the earth where it grows again, into a tree. So, theoretically, Mabon is the seed from the harvest that lays next to (or on) his mother, he then is absorbed into her womb and rebirthed.
Those were my ponderings anyhow.