From the Super Mario Wiki
A Kaboomba is a walking cannon enemy found in Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. They shoot cannonballs that explode after a few seconds. Kaboombas only appear in The Cave of the Mystery Maze and Raphael the Raven's Castle. Stomping them lets the player ride on them, and eating them does nothing. An egg or ground pound disposes of them.
The name "Kaboomba" is a portmanteau of the words "Kaboom!" (onomatopoeia for an explosion) and Goomba. Due to the Kaboombas' lack of similarities with Goombas, though, the name "Kaboomba" may just be a form of "Kaboom!". The Kaboomka Fireworks Factory was named in a similar style.
Names in other languages