Slang phrase nigger within the woodpile "a concealed motive or unidentified factor impacting a problem within an adverse way" [OED 1989] is attested by 1800; Thornton's "American Glossary" (1912) defines it as "A manner of accounting with the disappearance of gasoline," as a result "an unsolved secret.The slang expression "Niga" is really a remarka