An imperative found in Séadna is siúil leat abhaile. In An Músgraigheach, the Four Masters of Ballyvourney suggested correcting this to siúlaigh leat. That is as expected, but the full note says: nú, siúlaigh; nú thulcaig, nú thulcaid.

What is thulcaig and thulcaid? Could they be used in this context to be mean "get lost"?

Maybe there is a confusion in An Músgraigheach and these are alternative insults for "a bhacacháin" found a few lines down in Séadna?