I am searching for a book (preferably in Japanese, English also okay) on kanji and / or word etymology. Basically I am looking for something that explains the origin of words, for example: why is 馬鹿 written with horse and deer. Or why does 虹 consists of the insect radical. I know "学研新漢和大字典 普及版", but it's still too hard, so I am looking for something around the level JLPT-2. Children's books are also welcome of course ;) Thanks a lot!