Metaphors are used to convey one idea in a manner that is more easily understandable by a human, by attributing features to something that should not be taken literally. You may have noticed while using this strange language of ours that there are many metaphoric phrases that include parts of the body, such as head, eyes and neck.
Take the phrase ‘head of the table’, for instance. If the table were a person (and since we have named the upright posts of a table ‘legs’, that is a little easier to imagine), then the ‘head’ of that table would be the prime position, just as the actual head is on the human body. Similarly, you would refer to the person who is in charge of a faculty as the ‘head’ of that department, or the student performing the best in a group as the ‘head of the class’.
Why do we do this? For starters, we all have a human body (unless, you’re reading this in the far distant future where we’re all just brains in jars—if that is the case, welcome), so using a body part as a metaphor for something else is an easy image for everyone to conjure. When referring to a group of people or things, the word ‘body’ is often used, to give the impression that the group as a whole is important as a single entity, as is a body. An arm isn’t just good by itself, for instance, just as the first book of the Encyclopaedia Britannica by itself is also not much use. The collective is valuable as a whole, as is the human body. We humans often try to explain the world through the metaphor of our own bodies, it’s just been the way we’ve evolved our languages from grunts to perfectly formed sentences.
There are many phrases that include parts of the body, such as:
Eye of the storm
Having one’s hands tied
To stick one’s neck out
On one hand/on the other hand
To put one’s best foot forward
To let one’s hair down
Something costs an arm and a leg
Get to the heart of the problem
All these phrases include body parts to paint a better picture of the original meaning. For instance, the eye of the storm is generally physically circular, as is an eyeball; having one’s hands tied conveys the meaning of being physically held back or having limits imposed upon you; and if you have ever had long hair tied up all day, the feeling of letting it hang loose at the end of the day is relaxing, hence feeling free.