Various sources (such as Wikipedia) say that underlining words is a practice originally from handwritten documents, intended to show the printer that the words needed to be emphasized (with italics or some such). Today, I sometimes see underlines showing up in books and other printed material. When did books start using underlined text for emphasis?
Edit: Many of the answers and comments here seem to have a No True Scotsman problem. I’m well aware that good typography doesn’t use underlines for emphasis, but plenty of books use lousy typography.
Answer
In Western printing, underlining is at least as old as printing. There was a general process called rubricing which is the process of marking and annotating (originally by hand) of a printed manuscript to finish it and/or give more legitimacy to the printed item. Usually this was just red lettering, but very often included the use of underlining. Later it was common to forgo hand-rubricing in favor of a separate printing pass with red ink.
Try an image search for “rubricate underlining” and you will see examples.
Attribution
Source : Link , Question Author : Joe , Answer Author : horatio