Thanks for the link, K - I enjoyed this one, more of a test than some of Doc's recent offerings.
I quite agree about that abbreviation: not in Chambers that I can see, not in the IVR or internet suffix lists. Private Eye often refers to discussions of this nature, I believe!
The definition part is quite correct, though the word survives (in two or three letter form) in a very small number of Fenland, mainly S Lincolnshire, placenames. It has not - pace Chambers - been part of local dialect for many a long year. Certainly in the 1960s/70s when I lived there, the meaning of the word, and any certainty about its pronunciation, was lost even to elderly people.
Interestingly (or otherwise!) 'pattins', meaning (ice) skating - a word undoubtedly derived from French - was still going strong, though I guess it's less used now in the days of estuarine English and alleged global warming!