the.com/hatpin

means A long, sharp pin used to skewer a hat to a hairstyle so it wouldn't blow or bounce off.

from A straightforward compound of 'hat' and 'pin,' dating to the era when women's hats grew enormous and had to be spiked through piles of hair to stay put. As hats ballooned in the late 1800s and early 1900s, the pins lengthened to match — some reaching nearly a foot — and their sharpened points made them an obvious makeshift weapon, leading several cities to actually pass laws restricting hatpin length.