“While questions have clearly been around since time immemorial . . . the question mark has not. This handy graphic sign seems to have been formed from a Q with a little o under it as an abbreviation of the word quaestio (query, question). Similarly, the exclamation point—a.k.a., ‘screamer’ or ‘bang’—is derived either from an abbreviation of Latin interiectio (interjection) or else from the interjection Io! (‘Hey!’).”

—Alexander & Nicholas Humez, ABC Et Cetera: The Life & Times of the Roman Alphabet, 1985.