‘But it’s not just horses’
“Other animal behaviours too live on in our everyday speech. Even if few of us have ever literally taken ‘the bull by the horns’ or ‘bought a pig in a poke’ (what is a poke in this instance? a bag or sack, nowadays an obsolete or dialect word, so the phrase means ‘to buy something without seeing or being able to test it’) most of us flounder at times or try ‘to feather our nests.’” Christopher Levenson urges us to contemplate the origin of such phrases as ‘free rein’ and ‘ride roughshod over’ in his A Word in Your Ear essay ‘Animals and Language.’