"Reflection" originates from the Latin reflectere, meaning "to bend back" or "turn backward".  It combines the prefix re- ("back" or "again") with flectere ("to bend").  The term entered English in the late 14th century from the Old French reflecter, (turn back).  The original usage referred to mirrors and surfaces "shining back" light or sound waves.  The meaning later shifted to turning one's thoughts backward on themselves or reflecting upon matters.  It is closely related to "reflex," which also comes from the same Latin root indicating a backward bending or reaction. 

According to the Oxford English Dictionary (OED), the earliest known use of the noun reflection (or reflexion) in English dates to before 1398.   It appeared in a translation by John Trevisa.  The term refers to the action of throwing back light or heat and gained traction in Middle English.  The verb reflect was used slightly later, appearing before 1425 in Guy de Chauliac's Grande Chirurgie.   The earliest known use of the word reflective (as an adjective) is from the late 16th century, specifically cited in 1581 in the writing of Barnaby Rich.   The related verb reflect has earlier usage, dating back to the Middle English period (early 15th century).  Self-reflective was first recorded in 1670 in the work of Theophilus Gale.

Character reflection in stories is crucial for creating relatable, emotionally engaging narratives that allow readers to understand a character's inner life, motivation, and growth.  Through internal thoughts, feelings, and behavioral changes, reflection connects actions to themes, fostering empathy and making the story more meaningful.  

Just the facts:

REFLECTION Definition & Meaning - Merriam-Webster

REFLECTION Synonyms: 63 Similar and Opposite Words | Merriam-Webster Thesaurus

REFLEXION Definition & Meaning - Merriam-Webster

REFLECT Definition & Meaning - Merriam-Webster

REFLECTIVE Definition & Meaning - Merriam-Webster

SELF-REFLECTION Definition & Meaning - Merriam-Webster

LAW OF REFLECTION Definition & Meaning - Merriam-Webster

7 hours ago, drpaladin said:

Most begin their day in reflection, usually a mirror.

Usually true.

7 hours ago, Bill W said:

"Reflection" originates from the Latin reflectere, meaning "to bend back" or "turn backward".   It combines the prefix re- ("back" or "again") with flectere ("to bend").   The term entered English in the late 14th century from the Old French reflecter, (turn back).  The original usage referred to mirrors and surfaces "shining back" light or sound waves.  The meaning later shifted to turning one's thoughts backward on themselves or reflecting upon matters.  It is closely related to "reflex," which also comes from the same Latin root indicating a backward bending or reaction. 

7 hours ago, Bill W said:

     Character reflection in stories is crucial for creating relatable, emotionally engaging narratives that allow readers to understand a character's inner life, motivation, and growth.  Through internal thoughts, feelings, and behavioral changes, reflection connects actions to themes, fostering empathy and making the story more meaningful.  
     In addition, characters can serve as "mirrors" that reflect the traits or fears of the reader, making the story more engaging.   Reflections can also be utilized as a literary tool (or character type) to show the consequences of actions, serving as a warning or example of success/failure for the protagonist.  

Some of my favorite GA authors do this very well, including @Geron Kees, @Myr, @Bill W (especially in Bill W's short stories -- "Crash Landing" -- "My First True Christmas" -- and "A Gay Christmas Carol (Revised)"), @P. E. Knapp, @Laura S. Fox, @Mark Ponyboy Peters, @Dabeagle, @drsawzall, @Timothy M., and this list is getting too long, but also in some of my more recently discovered authors, such as @Jason Rimbaud, @Thirdly. and @Krista.   Good work, Authors on GA.