Why was Princess Peach originally called ‘Princess Toadstool?’
"Well, it turns out that in Japan, she was ALWAYS known as Princess Peach. But when Mario was introduced to the Western World, Nintendo America felt that ‘Peach’ was a bit odd and didn’t relate to anything else in the game. So, they opted to call her Princess Toadstool to relate to The Mushroom Kingdom.
Surprisingly, the name ‘Princess Peach’ wasn’t used officially until Mario 64."