Green’s Dictionary of Slang

nap n.2

[SE nap, (woollen) cloth that has a nap surface on it]

1. [late 17C–18C] a sheep; used only in phr. napper of naps under napper n.1 [note napper’s poll n.].

2. [late 19C+] (Aus.) in senses of bed or covering [SE knapsack; but note SE nap, a short sleep].

(a) a sleeping bag.

(b) blankets or some other covering used by a sleeper in the open-air, a pack (as used in Northern Territory).