Opening Umbrellas Indoors
You can thank the ancient Egyptians for this bad omen. They used umbrellas to protect themselves from the sun, but opening them indoors was considered an insult to the sun god.
It was equally as offensive to open one in an area that wasn’t sunny. Another theory traces it back to 18th century England when the mechanics of the “modern” umbrella made them straight-up dangerous when opened in close quarters.