Caption was a term used (especially in Scotland), for arrest or apprehension.^[1]

Caption also has an old legal use, to signify the part of an indictment, etc., which shows where, when and by what authority it is taken, found or executed; so its opening or heading. From this is derived the modern sense of the heading of an article in a book or newspaper.^[1]

In accordance with the American Heritage Dictionary, the word is still used in the United States to indicate: "the heading of a pleading or other document that identifies the parties, court, term, and number of the action."^[2]

The word is derived from old french caption or latin captio (as an adapted borrowing).