↑ The most common is the red king crab, also called Kamchatka crab or Alaskan king crab, as native to the far northern Pacific Ocean. It can reach a leg span of 1.8 m (5.9 ft).
↑ In https://www.websters1913.com/words/Horse, it reads: "Horse crab (Zoöl.), the Limulus; -- called also horsefoot, horsehoe crab, and king crab." Either king crab or horse crab is so big, hence the name.