Looking at his face, you may at first think that an elephant is a stolid animal, but if you observe his behavior for a while, you will soon realize that he is actually very quick-witted and sensitive.
stolidus (insensible, dull, slow, brutish, rude, stupid) (Latin)
dispassionate, impassive, imperturbable, stoic, stolid
Stone like: To be like a stone means you don't experience pleasure or pain. You are unaffected. It becomes 'T' SOLID. So someone very SOLID against 'T' (ears) or emo'T'ions. STOL (sounds like stool). and a stool is a nonliving thing without any emotion, similarly a STOLID person is like a stool, without any emotion, always dull and boring.