TRIVIAL PURSUITS: How did the hair pin get the nickname ‘bobby pin’?

But, why did the simple hair pin get the nickname ‘bobby pin’?

Hair pins are metal (or sometimes plastic) clips made with two flexible prongs, with one prong typically straight and one ridged.

Invented by cosmetics manufacturer Luis Marcus, the hair pin gained popularity during the Flapper era in post-World War I when short, bobbed hair became popular. Women used the pin to style their bobs and hold their short hair in place, hence giving way to the hair pin’s new nickname—the bobby pin.