From back + slash, because it is a slash “leaning back” against the direction of writing (in writing lines from left to right), in contrast to the more common (forward) slash / (“solidus, oblique, diagonal”). The actual direction of (hand-)writing these marks can be reversed, when writing from left to right, top to baseline: the backslash forwards, the (forward) slash backwards. The naming can be explained as an anthropomorphism, assuming a bar (|) standing on the baseline, facing in the direction of writing, toppling backwards or forwards, respectively. The (new) Unicode name of \ is REVERSE SOLIDUS.
1
The punctuation mark \ (a left-leaning diagonal line). (Common uses include (1) use as a delimiter in filepaths and (2) use as an escape character to mark literals.)
[…] I was trying to find a web-site for which I had been given the following address: http://www.isop.ucla.edu/pacrim/pubs/korjournal.htm. […] I began to work backwards, removing first the last part of the address following the last backslash (/korjournal.htm).2001, James T. Bretzke, Bibliography on East Asian Religion and Philosophy, Edwin Mellen Press, →ISBN, page 455:
“So, do what I tell you. Open a browser window and type this in the menu^([sic]) bar: F-T-P colon backslash backslash euronews dot net backslash...” I pecked carefully at the keyboard as he dictated a URL that was about fifty characters long, […]2010, Lee Vance, The Garden of Betrayal, Random House, published 2011, →ISBN, page 25:
1 more example
Also, avoid submenus^([sic]) that can confuse the audience—if you're giving lengthy Web site addresses full of backslashes, shorten it so only the Web site's home page is given.2010, Frank Barnas, Ted White, Broadcast News Writing, Reporting, and Producing, Fifth Edition, Elsevier, →ISBN, page 114:
From back + slash, because it is a slash “leaning back” against the direction of writing (in writing lines from left to right), in contrast to the more common (forward) slash / (“solidus, oblique, diagonal”). The actual direction of (hand-)writing these marks can be reversed, when writing from left to right, top to baseline: the backslash forwards, the (forward) slash backwards. The naming can be explained as an anthropomorphism, assuming a bar (|) standing on the baseline, facing in the direction of writing, toppling backwards or forwards, respectively. The (new) Unicode name of \ is REVERSE SOLIDUS.
1
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences To escape (a metacharacter) by prepending a backslash that serves as an escape character, thereby forming an escape sequence.