Chambers merely calls 'nesh' (dialect). Wiki gives various locations where 'nesh' is current, of which the nearest to Forest Of Dean is Shropshire; but it does also cite a usage from Hardy's The Woodlanders [among many other lit citations, of which Mary Barton seems to be the earliest], which would seem to put it nearer the Forest Of Dean, where I learnt from my late wife Valerie it was current. It was a word she much used of those [inc occasionally me!] reluctant to venture out in cold & rain &c.

~M~