The giant salamander is commonly called the "baby fish" because of its baby-like cry.
Tips
memory
Fish radical 鱼 plus 儿 'child' - picture a 'child fish'. The giant salamander 大鲵 is nicknamed 娃娃鱼 ('baby fish') because its call sounds like an infant crying, which lines up neatly with the 'child' part of the character.
register
The sense 'the female of certain fish' is literary and archaic, found only in classical texts. In modern Chinese 鲵 means the giant salamander, chiefly in the word 大鲵.
The fish radical 鱼 on the left marks 鲵 as an aquatic animal. Although the giant salamander is an amphibian, classical Chinese grouped it with fish because it lives in mountain streams.
The right side 儿 'child' supplies the sound (the older reading was close to ní). It doubles as a faint hint: the salamander's cry resembles a crying child, the very image behind its folk name 娃娃鱼.
