It (I suppose inevitably) cropped up a few days ago on a thread, that I forgot to remember - being very tired - that someone had had a white van man call "och aye, the noo" at him. Someone wondered what it meant. The answer is probably nothing, other than a survival of some long forgotten, and probably not very funny, music hall parody of the highlander in Glasgow - they were considered hysterically funny back around WW1, for some reason.

Anyway, the "..., the noo!" bit does actually make sense (just like the equally hysterical "..., at all, at all!" actually does). It's a translation of the Gaelic interjection "..., an drasda" - as in "mar sin leat, an drasd'" ("'Bye, for now!") - a sort of generally meaningless ending like "innit", "y'know", and so on.

Ah well! 'Bye, for now.