backslash (\) Definition - One of the many names for the \ symbol. It arose from the field of computer science in the latter half of the 20th century. Example - either\or Etymology - The first OED citation for the verb slash is from 1382 where it denotes "to cut with a stroke of a blade or whip." It perhaps derives from the Middle French esclachier, to break. Oxford English Dictionary - The first citation for the punctuation mark slash is from 1961; the first citation for backslash is from 1982: "…Arguments enclosed in backslashes refer to disk-file operations." (Byte Magazine, January 1982, 413/1 )