backslash แปลว่า

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.