put (one's) back up

1. To become angry, hostile, defensive, defiant, or irritable. John put his back up when his parents brought up the subject of college.

2. To cause one to become angry, hostile, defensive, or irritable. Election season always puts my dad's back up. Few things put my back up like hearing about a poacher killing an endangered animal.

get/put somebody’s ˈback up

make somebody annoyed: His silly remarks always get her back up.

This idiom refers to the way cats arch their backs when they are angry.