Go raibh míle maith agat!

Seriously, the chorus - sung to a man going on the run before invading soldiers, and probably, like most Irish aristocrats of the 17th-18th century, going off to be slaughtered in Europe fighting other people's wars, means:

Siúl, siúl,siúl, a rún
(Go, go, go, my darling)
['Siúl' literally means 'walk', but is used in some cases to mean 'go'; I remember being told sternly 'Siúl leat' - 'get walking', in effect - as a kid; 'a rún' literally means 'O secret', and is a standard term of affection]
Siúl go socair agus siúl go chiúin
(Go calmly and go silently)
Siúl go doras agus éiligh liom
(Go to the door and return to me)
Is go dtéirn tú, a mhúirnin, slán
(And may you return, darling, safe)