Did They Invent Hair Gel? Caesar’s Footprints: Journeys to Roman Gaul

Just a warning: nothing really to do with hair gel.

One minor tidbit:

  The Gauls [...] credited with the invention of 
  sapo, which was less an early form of soap, notes 
  Omrani, than a pomade that brightened the hair.

Everything I know about the ancient world I learned from Asterix.