The phrase “hair of the dog” is part of a longer expression “The hair of the dog that bit you”.
This saying goes back to an ancient belief that the hair of a rabid or other mad dog that bites someone could be used as an antidote against the bad effects of the bite. The hair (often burned first) was applied to the wound and was believed to heal the injury.
Thankfully, these days, “Hair of the Dog” simply equates to a brilliant dog grooming experience for your best friend……..