Alpha-sapphire: There is a bud on this Pokémon’s back. To support its weight, Ivysaur’s legs and trunk grow thick and strong. If it starts spending more time lying in the sunlight, it’s a sign that the bud will bloom into a large flower soon.Y: When the bud on its back starts swelling, a sweet aroma wafts to indicate the flower’s coming bloom.X: There is a plant bulb on its back. When it absorbs nutrients, the bulb is said to blossom into a large flower.
Prof. Lotus' Notes: The Bulbasaur line is an example of good video game design. Without the Red or Blue games implicitily telling you, Bulbasaur was the easiest option, Squirtle Medium difficulty and Charmander being most diffult because of the first two Gym Leaders being Brock (Rock Type) and Misty (Water).
Ivysaur is most likely a portmantaeu of Ivy and Dinosaur. It's Japanese name being フシギソウ (Fushigisou), a play on words of 不思議 (fushigi) 草 (sou) - strange grass. It's called Herbizarre in France.