the line Creach na Samhna also appears in a verse of An Duanag Ullamh the Matheson Collection; I have only skimmed it so far
https://digital.nls.uk/early-gaelic-book-collections/archive/76426180

see also pages 237-241 of Wilson McLeod's essay in "Fresche fontanis: Studies in the Culture of Medieval and Early Modern Scotland"
edited by J. Derrick McClure, Janet Hadley Williams (browsed via Google books)