Head Scratcher Meaning

(idiomatic) A particularly puzzling or confusing event.

Example: A device used to scratch the head.
  
2004, Kelley Hays-Gilpin - Ambiguous Images: Gender and Rock Art (ISBN number 0759100659) page 133.
  Her aunt's husband or her grandfather brings a head scratcher. "If the maid scratched her hair or body with her fingers during these days of observance, her hair would fall out."
December 2007, W:Daily News Tribune - Golden Globes nominations a head-scratcher
July 2002, Fox News - Attorney: Williams' Kids Near Compromise About Father's Remains
  "A judge will decide what is the most logical, although I'm sure to some judges [freezing the body] will seem like science fiction and a wild scheme," McDonald said. "Other judges make think this is a good thing. It will be a head scratcher for the judge."