The word closeness comes from the adjective close, which comes from Old French clos (meaning "confined, shut, or secret"), derived from the Latin word claudere (meaning "to shut").  Close was then combined with the suffix -ness, an old Germanic element used in English to turn adjectives into nouns that describe a state or quality.  It was first used to denote the state of being confined, enclosed, or kept secret.  The figurative sense applied to the nearness of persons developed by the 1560s, and the meanings related to being stingy (penurious) or meticulous appeared by the mid-17th century.  

According to the Oxford English Dictionary, the noun closeness was first used in English around 1443 during the Middle English period.  The word close first appeared in English during the Middle English period (1150-1500).  The earliest recorded evidence for the noun and verb forms of close dates back to before and around 1275

Closeness in storytelling builds deep empathy, creates emotional resonance and makes a narrative feel real by connecting the audience directly to the inner lives of characters.   

Why Closeness Matters:  
Empathy and Bonding: Physical and emotional closeness helps readers or listeners share what characters feel, releasing empathy-building responses in the brain.  
High Stakes: When characters share intimate truths, fears, or secrets, every plot twist or conflict hurts more and matters deeply to the audience.  
Immersion: A close narrative point of view lets people live inside the story world rather than just watching it from far away.  

How to Create Closeness:  
Sensory Details: Use sharp, small details like the sound of a voice or a nervous hand gesture.  
Inner Thoughts: Share private hopes, hidden flaws, and quiet moments of doubt.  
Vulnerability: Have characters open up honestly to one another without hiding behind a tough mask. 

Just the facts:

CLOSENESS Definition & Meaning - Merriam-Webster

CLOSENESS Synonyms: 191 Similar and Opposite Words | Merriam-Webster Thesaurus