Question: what ykk stand for on zippers?
Answer: Those letters stand for "Yoshida Kogyo Kabushikikaisha" which, from Japanese, roughly translates to "Yoshida Company Limited." It's a zipper manufacturer named after Tadao Yoshida, who founded it in 1934. By one estimate, the company makes half the zippers on Earth, which is more than 7 billion zippers each year.