hanky = handkerchief. (Bandanna)

I wear a Buff when my hair is at the awkward length that I like it best (long enough to create a rats nest, but too short for a ponytail with a helmet). I also have long bangs and it helps to keep those in check.

It also can help absorb the sweat that would drip into my eyes, if I position it so it's across the top of my forehead.