"Tenderness" (13th-14th century) originates from the Old French tendre (soft, delicate, young), derived from the Latin tener or tenerum (soft, delicate, young).  It is rooted in the Proto-Indo-European ten- ("to stretch"), suggesting a progression from "stretched" to "thin," "weak," and ultimately "delicate" or "youthful".  The suffix -ness was added to the adjective tender to denote the quality or state of being tender.  In the 13th Century, tenderness was used to describe softness, fragility, and youth.  In the 13th–14th Century, tenderness extended to mean "affection, loving kindness", and, in a physical sense it meant "sensitivity to pain. 

According to the Oxford English Dictionary, the noun tenderness was first used in English during the Middle English period (1150-1500), with the earliest known evidence appearing before 1382.  It was found in the Wycliffite Bible (early version).  Other sources, such as the Online Etymology Dictionary, indicate it was in use by the early 14th century, meaning "delicacy, sensitivity to pain". 

Tenderness in writing stories is the deliberate infusion of gentle affection, warmth, and care into a narrative, acting as a vital counterweight to conflict and trauma. It is essential for creating deeply relatable characters, fostering an empathetic bond with the readers, and providing emotional depth that makes a story memorable.  By focusing on vulnerability and human connection, tenderness transforms a plot-driven story into an emotional, resonant experience. 

Here is the importance of tenderness in writing stories: 
Forging Reader-Character Connection: Characters who exhibit tenderness—even amid conflict—become more three-dimensional and sympathetic. This allows readers to invest emotionally in the characters' fates, making them care more about the story's outcome. 
Balancing Emotional Arcs: While tension and conflict drive a plot, excessive, unrelenting negativity can lead to emotional exhaustion. Tenderness serves as a necessary "breather," providing contrast to intense moments and enhancing the overall emotional impact of the story. 
Enhancing Vulnerability and Realism: Writing with tenderness means showing the softer, unguarded moments of life. This creates a raw, real experience that resonates with readers because it mirrors the complexities of human emotion and relationships. 
Evoking Empathy and Affective Response: A tender, well-crafted scene can trigger a "gut" reaction in readers, making them feel the emotion rather than just reading about it. This emotional "holding" makes the narrative memorable. 
Deepening the Writer’s Voice: Approaching characters with care and, at times, vulnerability allows the writer's authentic voice to emerge. It requires the writer to "feel" the scene, bringing a layer of truth and compassion to the work. 
Cultivating Compassion: In a world that often prioritizes conflict, stories that include tenderness encourage understanding, compassion, and a deeper appreciation for the human condition. 

Just the facts:

TENDERNESS Definition & Meaning - Merriam-Webster

TENDERNESS Synonyms: 72 Similar and Opposite Words | Merriam-Webster Thesaurus

(I am wondering if I was the only dumb one who had to look up curated?)

15 hours ago, drpaladin said:

I carefully curated a steak for a month allowing it to age and season only to end up with meat with the tenderness of leather.

That’s because you were attempting to tenderize your steak into tenderness. (That never works.)

One must beat the meat into submission — that’s the only way! Gentleness only prolongs the endeavor.

Your end result may, of course, vary in its response … .