The word direction comes from the Middle English word direccioun, via the Old French word direccion,  It traces back to the Latin noun directionem, meaning "a straight line or alignment".  The Latin noun was formed from the past participle of dirigere ("to set straight or arrange"). 

According to the Oxford English Dictionary (OED), the noun "direction" was first used in English around 1425 in the writings of English poet and prior John Lydgate.  Originally, the word direction was used to describe the physical act of guiding or pointing something out.  In the early 15th century it gained meanings tied to management, administration, or official orders/instructions.  In the 1590s it began to mean specific instructions on how to reach a destination.  And in the 1660s it expanded to describe the literal course of a moving object or a relative spatial position without distance.  

Direction in storytelling gives a narrative clear momentum, preventing it from feeling aimless and ensuring that characters, plots, and emotional arcs move toward a meaningful destination.  

Why Direction Matters:  
Creates Reader Investment: A clear character goal or trajectory tells the audience what is at stake, making them care about the outcome.  
Drives Momentum: Turning points and conflicts act as navigational tools that push a protagonist forward or force them to adapt, preventing a sagging middle.  
Provides Displacement: Like a vector in physics, a story with direction ensures the audience ends up somewhere new emotionally or intellectually rather than looping in place.  
Maintains Focus: Clear orientation regarding who, when, and where keeps the audience from getting lost in unnecessary details.  

Pitfalls of Lacking Direction:  
Flat Characters: Without obstacles and changing directions, characters fail to grow or transform.  
Aimless Flow: Stories that lack a definite path suffer from random jumps or redundant descriptions that confuse the reader.