Medieval manuscripts are full of strange squiggles used to abbreviate words or word endings. It's almost like reading shorthand. Here is a short list for Middle

Medieval manuscripts are full of strange squiggles used to abbreviate words or word endings. It's almost like reading shorthand. Here is a short list for Middle English [1] but for Latin there were dozens if not hundreds. So I'm not surprised that + and - originate from that time. [1] http://isites.harvard.edu/fs/docs/icb.topic453618.files/Central/editions/paleo.html#abbrev http://isites.harvard.edu/fs/docs/icb.topic453618.files/Cent... EDIT: In fact, the second symbol on that list, the abbreviation for "and," seems half-way to becoming a +.