In his essay "Politics and the English Language," George Orwell criticizes the use of what he calls dead metaphors. These are metaphors that have become so worn-out and overused that they no longer hold the same evocative power that they once did. In fact, many of these metaphors are so overused that people may not even realize that they are metaphors in the first place. According to Orwell, the use of these metaphors is a sign of a lazy or uninformed writer.
Orwell provides a number of examples of dead metaphors in his essay. These include
Ring the changes on, take up the cudgel for, toe the line, ride roughshod over, stand shoulder to shoulder with, play into the hands of, no axe to grind, grist to the mill, fishing in troubled waters, on the order of the day, Achilles' heel, swan song, hotbed.
There are many other dead metaphors that can be included as examples. Think of terms that are regularly used yet seem to have little meaning on their own. Examples could include the following.
Deadline: This originally referred to the perimeter of a prison that a prisoner was forbidden to cross or risk getting shot. Now it is used to mean a time by which an assignment is due.
Nose to the grindstone: This is a phrase that originally referred to the practice of smelling the milling of wheat to keep it from burning. Now it means to work hard while paying full attention to a task.
Loose cannon: When a cannon aboard a ship broke free of its ropes during a storm or battle, it would potentially become a danger to the ship and the crew. This metaphor has lost its nautical meaning and now refers to a person who is a risk to themselves or others around them.
Cover your bases: This is a reference to a situation in baseball in which fielders prepare for any hit by making sure each base is accounted for. Today, it simply refers to having multiple contingency plans in order to assure success.
As you can see, these figures of speech are so outdated and overused that they cease to have much, if any, connection to their original meaning.