Butter substitute margarine was originally developed from nuts, so why didn't they call it "nutter"?

Turns out they did. The brand name of an early version of the then-controversial spread was indeed called "Nutter".

From the Daily News Cookbook, UK. Can't find a publication date but the paper itself was founded by novelist Charles Dickens in the 1840s and folded (in the economic sense) in the Depression of 1930.