It says "トノサマ". There are many explanations for why "frog" is pronounced "カェル". Some people say that frogs return to the place where they were born (in the water) when they lay eggs, so they are called "return". Some people say that frogs are hatched from eggs, so they are called "hatching". Some people say that in ancient times, frogs were superstitious about changing the weather, so they were called "ぇる". Some people say that frogs were called "カヒル "→" カェル ".Some people say that frogs can be resurrected by wrapping them in banana leaves when they are dead.
There are all kinds, and I don't know which one is right. One thing is certain: "カェル" has a history of thousands of years. There is a poem in Ye Wan Ji: My householder turned yellow into shrimp, and no one saw his sister (I am がやどにもつかへる) and was indifferent to the sun.
Note that "shrimp hand" refers to "maple leaf". Because the shape of maple leaf is very similar to that of frog's paw, "maple leaf" is pronounced as "かぇで" in Japanese, and the word comes from "カェルて".