Slang phrase nigger during the woodpile "a hid motive or not known factor affecting a scenario in an adverse way" [OED 1989] is attested by 1800; Thornton's "American Glossary" (1912) defines it as "A manner of accounting for the disappearance of gasoline," as a result "an unsolved secret.They applied samurai swords, shurikens, together with other