What nickname did young US Navy pilots give the Corsair because it was so hard to land on a carrier?

Early Navy pilots called the F4U the "hog," "hosenose," or "bent-wing Widow Maker." It was also known as the "Ensign Eliminator," and for good reason.

The fuel tank located in front of the pilot pushed the cockpit far back in the fuselage, which limited visibility on the landing approach. The long "hose nose" and the Corsair's nose-up attitude made it hard to see ahead. The "birdcage" canopy, with its struts, offered insufficient visibility for taxiing on deck. The visibility problem was solved by having the Corsair approach the carrier from the eight o'clock position and enter the final leg with a wide left-hand turn.

The oleo struts of the landing gear had poor bounce characteristics on landing, which allowed the aircraft to go bouncing across the carrier deck. The gear was too stiff, and the Corsair tended to bounce on the deck and then dig its nose into it. During slow carrier landings, the left wing could stall and drop quickly and without warning. If power was applied suddenly, the left wing could stall and drop so fast that the fighter would flip over. That tendency to stall on the left wing first resulted in a deadly snap roll.