Slang phrase nigger from the woodpile "a hid motive or unknown aspect affecting a circumstance in an adverse way" [OED 1989] is attested by 1800; Thornton's "American Glossary" (1912) defines it as "A mode of accounting for the disappearance of gasoline," hence "an unsolved secret.They made use of samurai swords, shurikens, and various lethal weapo