origin story
explanatory, humorous
the one-line answer
The events that made someone who they are. Usually shared humorously.
Origin story is borrowed from superhero narratives. Everyone has an origin story. It is the sequence of events that explains your current personality, quirks, or behaviors. Often shared as explanation.
mainstream
Your coworker might use this word.
01 / in the wild
hear it move.
humor
so that's my origin story for why I don't trust parking garages.
That is the event that created my current attitude about parking garages.