nig-nog n.

"foolish person," 1953, OED suggests from earlier cant slang nigmenog "a very silly fellow" (1700). Compare Australian and dialectal ning-nong "fool" (1832). The word turns up in various apparently unrelated contexts in late 19c.-early 20c. Wright's "Dictionary of Obsolete and Provincial Words" (1886) has nig-nog as a verb for "to fuck." It also was the name of a fictitious patent medicine that "cures all nervous ailments," etc. in a humor story by Edgar Wallace originally published in 1923. As a term of abuse for a black person (by 1959), a shortened and reduplicated form of nigger.