Pokemon name meaning:
ケロケロ kerokero – frog sound
泡沫 houmatsu – bubble on the surface of liquid.
Keromatsu is described as a “bubble frog pokemon” so the name contains both elements.
“Kero kero” is the Japanese equivalent of “ribit ribit” and frogs are often referred to as “Kero-kero-san” by children (similar to Wan-wan-chan for a dog, which is equivalent to calling it a woof-woof). Kero is close in sound to the real word for frog, which is カエル kaeru.
Hello Kitty’s frog friend is called Kerokerokeroppi, a familiar example of the use of kero-names for frogs in Japanese popular culture (the ppi is a cute pseudo-honorific nickname ending).