Before any actual character development, Wario's name was the first thing that was decided on, being derived from the Japanese word 'warui' (悪い), meaning 'bad'. It was initially director Hiroji Kiyotake's idea to introduce Wario as a new character that fits this change in objective, although several rejected characters were presented earlier which no one took a liking to.
Super Mario Land 2: 6 Golden Coins official Shogakukan game guide, staff interview on pages 106-111 ( translation provided by 'Shmuplations', accessed September 10, 2016) Rather than having Mario fight for the benefit of someone else (such as Princess Daisy in Super Mario Land 2's precursor, and Princess Peach throughout other games), the staff wanted Mario Bros to fight to win back something of his own. The staff team aimed for a 'change of pace', and to not be bound by the ideas which were continuously used in Mario games leading up to that time they desired to provide Mario with a new objective. The idea to introduce Wario as a new character originated during development of Super Mario Land 2: 6 Golden Coins.
