M-W's Word of the Day for All Y'all Late Antique and Numismatic Types

solidus \SAH-luh-dus\ noun

1 : an ancient Roman gold coin introduced by Constantine and used to the fall of the Byzantine Empire
*2 : a mark / used typically to denote "or" (as in and/or), "and or" (as in straggler/deserter), or "per" (as in feet/second)

Example sentence:
In her latest thriller, the author manipulates her readers into believing there are two killers until the final page, where she connects their two names with a solidus.

Did you know?
Call it a solidus, or call it a slash/diagonal/slant/virgule — whatever you call it, you are bound to run into this useful mark with some regularity. These days, one place the mark is commonly seen is in Internet addresses (http://www.merriam-webster.com/cgi-bin/mwwod.pl, for example), but the history of the word "solidus" takes us back to a time well before computers. The ancient Roman emperor Constantine the Great borrowed the Latin term for "solid" ("solidus") for the gold coin that was the successor to the aureus. And in Medieval Latin, "solidus" designated the shilling. Before the introduction of decimal coinage, abbreviations of the shilling ("s," "sh," or "shil") were used. Eventually, the abbreviations were replaced with the simple symbol "/," which became known as a solidus.

*Indicates the sense illustrated in the example sentence.

I never knew that the mark '/' was called a solidus. So perhaps now we should begin saying things such as 'The web address is aitch tee tee pee colon solidus solidus...'?