Why can I not find "dunamany" in any on-line dictionaries or etymologies?

I was talking about something and used the word “dunamany”, which I understand to be an adjective meaning “a lot” or “many”.

When challenged, I couldn’t find it in any on-line dictionaries or etymologies, although I did find it used in a few places on-line, if you google “dunamany”.

So why can’t I find this word on-line in a dictionary or etymology?

It seems to be a word in a dialect of Scotland.

Surely the etymology is from “(I) don’t know how many.” Perhaps you can’t find it as it’s a phrase, not a single word.

It’s in the OED (with a double-n spelling):

interesting - thanks. Still doesn’t show up in Etymology Online, though.

Another new word for me today. Thanks all.

No, its sussex slang.

Interesting. Yes, dunnamany is Sussex slang, but the OP asked about dunamany (one “n”) which does appear to be Scottish Highlands slang.

A probably supremely useless bit of information, concerning the 1946-published “young adult” novel Mistress Masham’s Repose, by the British author T.H. White, best known for his The Once and Future King treatment of the Arthurian legends. MMR is set in the county of Northamptonshire, in the East Midlands of England; and includes a passing reference to the imaginary village in that county, of Dunamany [one “n”] Wenches.

Also appears in several Scottish historical romance novels by Amanda Scott.

Also appears as a place name of Dunamany, Parish of Donaghkeady, Ireland.
(Proceedings of the Royal Irish Academy
Hugh W. B. Thompson
The Irish Church Quarterly
Vol. 10, No. 40 (Oct., 1917), pp. 310-312
)

In my Shorter OED, the origin of dunnamany is listed as ‘Repr(esentative of) informal pronunc(iation).’