In substitution type of questions, some particular objects are assigned code names. Then a question is asked that is to be answered in the code language.
If finger is called toe, toe is called foot, foot is called thumb, thumb is called ankle, ankle is called palm and palm is called knee, which one finger has a different name ?
Clearly the 'thumb' is a finger having a different name.
But 'thumb' is called 'ankel'.
So, 'ankle' is the finger that has a different name.