ninja adj. OED has 1966 1959 Alex C. D. Noe, Above the Rim and Other Poems 16 Just take a ninja rubber ball An’ bounce it up an’ down, nat’s all. https://archive.org/details/aboverimotherpoe0000alex/page/15/mode/1up?q=ninja ------------------------------------------------------------ The American Dialect Society - http://www.americandialect.org