Punctuation: Names of marks
From Why We Punctuate by William Livingston Klein and English Grammar; Punctuation and Capitalization; Letter Writing published by The International Textbook Company:
The names of the principal marks were given to them by the Greek grammarians. The name of each mark is the name of the group of words with which the mark was used.
I. Period (.)
John went home.
The period (periodos, “a way around”) marked a complete circuit of words, and the picture in the word is the circular track of a race course.The group of words which we call a sentence, the Greeks called a period. They arbitrarily marked its end by a dot, and called the dot also a “period.” We retain the name of the mark.
II. Colon (:)
John took with him his tools: hammer, saw, level.
The colon (kolon, “a limb,” “half of a race course”) was one of two main divisions of a long compound sentence. From the part or division the name was transferred to the mark used in indicating the divisions. We retain the name of the mark in our word colon.
III. Semicolon (;)
John dropped the hammer on his toe; it hurt badly.
The semicolon is a mark of later date; and, as its name implies, it falls between the comma and the colon in its character and use. Strictly, the semicolon should be used in separating a sentence into fourths; but, for obvious reasons, no such limitation is possible. It indicates a degree of separation less than that made by the colon, but only in name, not in reality, is it a half-colon.
IV. Comma (,)
John hopped, howled, cried, and cursed.
The comma (komma, “a segment;” koptein, “to cut”) denotes the shortest separation in ideas or construction between sentence elements.
IV. Question mark (?)
Had John broken his toe?
The question mark is said to have been made from the initial and final letters of the Latin word Questio, the Q being written above the o; thus,
John had broken his toe!
The exclamation mark is believed to have been formed from the letters of the Latin interjection io, expressing joy; thus,
