Harpina (or Harpinna) was, according to some accounts, the mother of Oenomaüs, king of Pisa. The name was also that of a mare owned by Oenomaüs. It can mean either 'snatcher', from harpazo (see Harpies) or more likely 'falcon', from harpe.
This would be a good descriptive name for a horse that was very swift (as the Harpies were). Admittedly, it is less fitting when applied to Oenomaüs' mother.