Origins
The headline as we know it — large, bold, attention-grabbing — is barely a century old. The word itself dates to the 1670s, but it originally meant something quieter: the running line at the head of a printed page, showing the page number and chapter title.
For most of newspaper history, articles opened with 'headline decks' — stacks of small, modest lines that summarised the story in descending detail. A single article might carry six or seven headlines, each in standard-sized type. Nobody was shouting.
That changed in the 1890s. Joseph Pulitzer's New York World and William Randolph Hearst's New York Journal were locked in a circulation war. Both papers began using enormous headlines — sometimes spanning the full width of the page — to catch the eyes of passers-by at news-stands. The era of yellow journalism gave birth to the modern headline.
Proto-Indo-European Roots
The compound is straightforward: head (the top) + line. Head descends from Old English hēafod, from Proto-Germanic *haubudam, from Proto-Indo-European *kaput- ('head'). The same PIE root produced Latin caput, which gave English captain (head of a company), capital (head city), and chapter (a 'head' section of a book).
The verb headline ('to headline a concert') is 20th-century, borrowed from entertainment billing where the headliner's name appeared at the top — at the head of the line.