Aha. So "Seo libh canaig" is "Here with us, chant" - the "chant" being an order - gwan, chant, willya. "Buionn dar slua" seems to be "a hosting of that band" (in the sense of a band of comrades, not a band of Mudcatters playing their band-jos).
"Buionn dar slua" seems to be "a hosting of that band" (in the sense of a band of comrades, not a band of Mudcatters playing their band-jos).