Palaemon means 'wrestler', from palaio, 'to wrestle'. It was the name of several characters, including the son of Heracles and Autonoë (whose father certainly 'wrestled' with many a task), the son of Hephaestus (again for the exploits of his father), and (as a new name) Melicertes, son of Athamas and Ino, who aided sailors in distress. With regard to the first of these three, it should be remembered that Heracles was actually called Palaemon originally.
As for Merlicertes, the new name was acquired at the same time as the conversion of his mother Ino to the sea-goddess Leucothea. It was given him by
Sisyphus, who made the newly named Palaemon the protector god of the so-called Isthmic Games (those held on the isthmus of Corinth).
