Mike Wehner writing for TUAW:
[…] the story goes that when Steve Jobs first saw the keyboard command list for MacDraw he was unhappy with the number of Apple logos cluttering up the list, as the Apple symbol was used on the keyboard’s action key. He demanded that his team find a suitable symbol to replace it.
Apple’s bitmap artist, Susan Kare, immediately began browsing for a new icon and stumbled upon the familiar symbol, which is used on modern roadside signs in Scandinavia to highlight a point of interest or cultural heritage. She presented the symbol to the team, they squealed with delight, and the Command key as we now know it was born.