Since ancient times, "six" has often been used in "six directions" and "six great things," which represent nature or the world, and "six virtues" and "six laws," which represent providence or law, and can be said to be a harmonious number with neither too much nor too little. "Gen" refers to a bundle of thread dyed a deep, rich black. By extension, it has the meanings of "profound," "deep," and "quiet." A person with skilled techniques and knowledge is called a "professional," and "six gen" refers to a harmonious sake made by the skilled techniques of a master brewer.