Re: "fit" (and noting what Malcolm Douglas writes about Buchan &c pronunciation), in a song dating back until at least the C18, "Jockey said to Jenny" the same construction appears, with the sense "not at all", "forget it", "no way, pal". Jockey wishes to marry Jenny:

"Jockey said to Jenny,
'Jenny, will thou dae't?'
'Ne'er a fit," said Jenny,
'For my tocherguid,
For my tocherguid,
I winna marry thee;'
'E'en's ye like' quo' Jockey,
'I can let ye be..."

(a "tocherguid", sometimes "tocher guid", is a dowry or "fortune")