Editor’s Note: Read more unknown and curious design origin stories here.

CNN  — 

On Good Friday 1958, thousands gathered in London’s Trafalgar Square to protest nuclear weapons. They were responding to a string of test blasts conducted by the United Kingdom, the third nation to join the nuclear club after the US and USSR.

For the next four days, the bravest among them marched to Aldermaston, a small village 50 miles west of London where British nuclear weapons were designed and stockpiled.

On the protesters’ signs and banners, a new symbol was making its first appearance. Gerald Holtom, a designer and a pacifist, had developed it specifically for the march just a few weeks prior. He believed that a symbol would make the message stronger.

He was right: The symbol was adopted soon after by the Campaign for Nuclear Disarmament (CND) and went on to become one of the most widely recognized designs in history.

“It’s a minor masterpiece with major evocative power,” said design guru and cultural critic, Stephen Bayley, in an email. “It speaks very clearly of an era and a sensibility.

“It is, simply, a fine period piece: the ordinary thing done extraordinarily well.”

Semaphore alphabet

The design is meant to represent the letters “N” and “D” – standing for “nuclear disarmament” – as they appear in the semaphore alphabet, which is used by sailors to communicate from a distance with flags.

But there’s another meaning, according to its creator. In a letter to Hugh Brock, editor of the British magazine Peace News, Holtom wrote: “I drew myself: the representative of an individual in despair, with hands palm outstretched outwards and downwards in the manner of Goya’s peasant before the firing squad. I formalized the drawing into a line and put a circle round it.”

The symbol has been the subject of various different interpretations since its inception. “All good graphic devices should be lucid and capable of applications in different media,” said Bayley. “But this one has the advantage of a nice semantic ambiguity: It can be read in different ways. A missile at lift-off? A person waving in despair? A Druidical reference? But it bypasses interpretation: It’s a thing unto itself.”