or back sto·ry

[bak-stawr-ee, ‐stohr-ee]
noun, plural back·sto·ries.
  1. a narrative providing a history or background context, especially for a character or situation in a literary work, film, or dramatic series.
  2. prequel.

Origin of backstory

1980–85; back1 + story1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for backstory

Contemporary Examples of backstory

Word Origin and History for backstory

c.1990, from background story.

Online Etymology Dictionary, © 2010 Douglas Harper