I think you have to use your body to get the full feeling that the words imply. Breathe in, holding as much in as you are capable of (harder for some of us than others) then clench everything that can be clenched, then try to talk to yourself in the mirror. Then think of a word to describe yourself. Then I don't think you need to wonder why so many words and phrases referring to a certain rigidity of personality, spring from roots associated with the same area of the human anatomy.