There’s nothing quite like etymology for reminding us that computers have a history like everything else: one full of human decisions, revisions, eccentricities and whims.

Having written about the unexpectedly intricate history of @, I thought I’d turn to a more unlikely digital icon—Apple’s command key, marked by a square with looped corners, or ⌘.

Known sometimes as the St John’s Arms, it’s a knot-like heraldic symbol dating back in Scandinavia at least 1,500 years, where it was used to ward off evil spirits and bad luck. A picture stone discovered in a burial site in Havor, Gotland, prominently features the emblem and dates from 400-600 AD. It has also been found carved on everything from houses and cutlery to a pair of 1,000-year-old Finnish skis, promising protection and safe travel.

1,500-year-old Picture Stone from Havor (with stylized serpents below)

It’s still found today on maps and signs in northern and eastern Europe, representing places of historical interest. More famously, though, it lurks on the keyboard of almost every Apple computer ever made—and in Unicode slot 2318 for everyone else, under the designation “place of interest sign.”

So how did ⌘ make the leap from mystical inscription to a key of its own?

The answer, according to original Macintosh team member Andy Hertzfeld, is graphic designer Susan Kare. In 1983, a software meeting at Apple HQ was interrupted by Steve Jobs, who had discovered that Apple’s own brand symbol appeared next to every single item on an application’s menu. This was, he declared, “taking the Apple logo in vain!”—an unacceptable excess.

Thus it was that the company’s resident bitmap artist, Kare, found herself thumbing through an international dictionary of symbols looking for a fresh sign that was “distinctive, attractive and had at least something to do with the concept of a menu command.” The St John’s Arms fitted the bill—and, one swift bitmap design later, the command key was born.

We have a lot more to thank Kare for than just command symbols, however. As a fascinating look at her sketchbook by author Steve Silberman shows, her work on the interface of the 1984 Apple Macintosh helped define the first face of personal computing as something genuinely, well, personal.

In addition to designing one of desktop computing’s first proportionally spaced digital fonts, Kare originated the now near-universal conventions of a brush for “paste”, a pair of scissors for “cut”, the original bitmap for Apple’s own logo, a tiny rubbish bin for “trash”, and dozens of other visual touches that helped turn a screen into somewhere ordinary users felt fully at home.

Kare’s original command key bitmap

Graphical use interfaces had existed before, but they had never commanded a general affection to match the eagerness of early adopters. Much like a good map, Kare’s designs helped transform this by providing something beyond information: a human elegance echoing the Mac’s intuitive philosophy of design. As she explained in an interview marking the Mac’s 30th birthday:

It was explained to me that the Mac’s intended audience was non-technical, and that the interface should look so friendly and be so easy to use that “your mom could do it”… Another prevailing idea was that it would be ideal if a user could just figure things out without a manual, as in an arcade game. I interpreted “personal” and non-technical to mean that it would be good if symbols were based on everyday objects, when possible. For example, it seemed to me that more people had experience with a wristwatch than an hourglass…

Here was a digital geography offering opportunity, personality and places of interest—welcoming explorers with the promise that they would come to no harm. Needless to say, given the history of ⌘, it worked like a charm.

(For those interested in further etymological explorations, my book Netymology has a rich supply.)