It's a night visiting song, the laird is doing a bit of nocturnal courting,
            " I've had mair than thirty fa's,
             Coming out ower the plain"

I've fallen more than thirty times, on my way here across the plain.

The reason he's fallen is the night is dark and the ground uneven, he has not travelled by road but across the plain.

The chorus then goes "Let me in this ain night
                            or I'll no be back again"

If memory serves the next verse goes on to describe how he's cold and frozen, so he got muddy and soaked to the skin as he fell the thirty or more times and is now begining to freeze.

Not a pritty picture perhaps, but if it gets him over the door, (or through the wimdow), I'm sure he'll think of somthing to warm him.

cheers, John