A lake-burst (Old Irish: tomaidm[1]) is a phenomenon referred to in Irish mythology, in which a previously non-existent lake comes into being, often when a grave is being dug. Part of the lake-burst stories may originate in sudden hydrographic changes around limestone-based inland plains or turloughs. […]
Medieval bards had a special genre of lake-burst poems called tomamond.
Source: Lake-burst – Wikipedia
Tim B.
“Apparently, medieval Irishmen were convinced that almost all of their lakes had emerged after Noah’s flood. Their myths suggest that land reclamation and deforestation went hand in hand with the seasonal inundation of low-lying plains.”
Tim B.
https://en.wikipedia.org/wiki/Dwyfan_and_Dwyfach