How did Rainsford end up on Ship-Trap Island? What is the meaning of he island's name?

The poor guy fell overboard while cruising the Caribbean in his yacht one night. The engines were noisy, and no one could hear him.......... so he had to swim ahore to the island or risk drowning. Once ashore, he falls asleep on the beach.

The island got its name because of all the ships that ran aground there, and all of the sailors who found themselves stranded there.