Green’s Dictionary of Slang

napping cove n.

[nap v.1 (6) + cove n. (1)]

(UK Und.) a watchman; by ext. a hue and cry.

[UK]J. Shirley Triumph of Wit n.p.: The Napping-Cove is hood-wink’d The Hue and Cry is belated.
[UK]Dr Saman Golden Cabinet of Secrets [as cit. 1707].
[UK]Scoundrel’s Dict. [as cit. 1707].