Green’s Dictionary of Slang

1. (UK Und.) butter.

1610		Rowlands Martin Mark-all 41: Spreader butter.
1741		Canting Academy, or the Pedlar’s-French Dict. 111: Bread and Butter, Pannum & Spreadum.

2. (N.Z.) a blanket.

1845		Bolton Chron. 7 June 4/2: [of NZ] Every article of trading had its slang term [...] Thus pigs and potatoes were respectively represented by ‘grunters’ and ‘spuds,’ guns, powder, blankets, pipes, and tobacco, by shooting-sticks, dust, spreaders, steamers, and weed.
2003		McGill Reed Dict. of N.Z. Sl. 197: spreader A blanket, used by whalers here before it was recorded elsewhere.