What’s the origin of the phrase ‘Put your back up’?
This term derives from the habit of cats of arching their backs when threatened or annoyed. It is a British colloquial phrase and came into being in the 18th century. An early example of its use is from Grose’s Classical Dictionary of the Vulgar Tongue, 1785:
BACK UP. His back is up, i. e. he is offended or angry: an expreffion or idea taken from a cat; that animal, when angry, always raifing its back. An allufion alfo fometimes ufed to jeer a crooked man; as, So, Sir, I fee fomebody has offended you, for your back is up.