One Piece Chapter 2, page 15: THEY CALL HIM "STRAW HAT LUFFY"

Alvida and her crew surround Luffy and Koby. Alvida asks, "IS THAT THE BOUNTY HUNTER YOU HIRED? WELL, HE CERTAINLY ISN'T RORONOA ZOLO... SO I'LL GIVE YOU ONE CHANCE TO REPENT... WHO IS THE FAIREST THROUGHOUT ALL THE SEAS? ANSWER ME!!!" Luffy looks at Alvida, points his finger, and asks, "HEY, WHO'S THAT TOUGH-LOOKING OLD BIDDY?" The entire crew and Koby burst out in shocked laughter and panic, with Koby screaming, "LUFFY!! TAKE IT BACK!! NO WAY!" Alvida growls in absolute fury.