The punctus exclamativus (or punctus admirativus) first appeared in the latter half of the 14th century to mark the end of an exclamation. The Italian poet Iacopo Alpoleio da Urbisaglia claimed to have invented it. The influential Italian humanist Coluccio Salutati revived the exclamativus and its use spread in the 15th century.
Although the exclamation goes by many names, in the American typographic and printing trades, the exclamation point was referred to as a “bang” or a “screamer.” Bang still exists in programming, as in “Postscript files always start with percent-bang-PS” (%!PS).
Traditional etymologies of the exclamation mark, recounted by the brilliant, amateur classicists, Alexander & Nicholas Humez in their book ABC et Cetera go like this:
“…the exclamation point … is derived either from an abbreviation of Latin interiectiō (interjection) or from the Latin interjection Iō! (‘Hey!’).” In their most recent book, On the Dot, the Brothers Humez explain that the exclamation mark was known in English as “note or mark of admiration (a straight-forward translation of Iacopo’s term punctus admirativus),” and the term “exclamation point” was adopted in the 17th century.
If you accept the traditional etymologies, the morphology of the exclamation point, as with the question mark, appears to boil down to the convenience of abbreviation. Medieval scribes stacked the i above the o, the o became a point, and thus evolved this energetic punctuation mark.
Note: Avoid overuse
Our advice: exclamations should not be used in business correspondence, but online communications have made this once rarely-used punctuation mark all too common, and (along with emoticons) they’ve slipped across the blurred boundaries of every form of electronic communication.
“Cut out all these exclamation points. An exclamation point is like laughing at your own joke.”
—F. Scott Fitzgerald
“Keep your exclamation points under control. You are allowed no more than two or three per 100,000 words of prose.”
“So far as good writing goes, the use of the exclamation mark is a sign of failure. It is the literary equivalent of a man holding up a card reading ‘laughter’ to a studio audience.”