Rainsford is speaking with his friend, Whitney, at the very beginning of the story. Whitney tells him about the island and says that it has become the subject of sailor lore. He says,
"This island has an evil name among seafaring men." (pg 1)
The men are jumpy, and Rainsford notices that even the captain, a tough old guy, is jumpy too. Whitney asks Rainford if he doesn't feel something strange in the air,
".....as if the air were actually poisonous" (pg 1)
Rainsford has to admit that he does feel a sudden chill, a mental chill,
".... a sort of sudden dread (pg 1)
The name that was written on the chart for this island is Ship Trap Island. This makes a lot of sense considering the fact that Zaroff uses lighthouse lights to direct the ship's off course and into the rocks. When he shows Rainsford the lights, Zaroff says,
"They indicate a channel where there's none; giant rocks with razor edges crouch like a monster with wide-open jaws. They can crush a ship as easily as I crush this nut." (pg 7)
You can see why the name was given to the island, and why the sailors have made it part of their sailor lore.
My copy of the story is from the internet. If yours is in an anthology or book, it may have different pages.