Nematomorphs are commonly called horsehair worms. Their name stems from the once-held belief that these slender, cylindrical worms, observed in horse-watering troughs, spring from horsehairs. Adult nematomorphs coil and tangle with each other, so they are also known as gordian worms, after Gordius, king of Phrygia. Gordius tied a knot, declaring that whoever untied his intricate knot should rule Asia. Alexander the Great cut the Gordian knot with his sword and added Asia to his Greek Empire.