The “hair of the dog that bit you” is a colloquial Scottish expression based on the superstition that applying a souvenir from that vicious animal to a wound would help the healing process, according to E. Cobham Brewer’s Dictionary of Phrase and Fablefrom 1898. Over time, the saying was repurposed to symbolize a hangover cure and then, in April 1975, became the name for Nazareth's sixth studio album.

That's not how it started out, though. Former frontman Dan McCafferty later confirmed that the eponymous opening cut on Hair of the Dog – in which a dishonest young woman (an “heir of the dog,” if you will) finally meets her match – provided the original album title with its recognizable chorus of “now you’re messing with a son of a bitch!”

Nazareth’s record label, of course, wasn’t about to let them name the project Son of a Bitch. So, Hair of the Dog was selected as a compromise, putting the finishing touches on a career-defining release.

Produced by guitarist Manny Charlton, after three LPs overseen by Deep Purple bassist Roger Glover, Hair of the Dog was chock-filled with sharp-toothed blues rockers like the power chord-driven “Miss Misery,” the elastic-riffed “Changin’ Times” (which took Led Zeppelin and made them ballsier), and the exceptionally fierce “Beggar’s Day” (which in turn may have set a blueprint for AC/DC). All of them were tailor made for real and air-guitarists everywhere.

Listen to Nazareth Perform 'Love Hurts

Elsewhere, Nazareth transformed Randy Newman’s “Guilty” into a desperate gospel-soul plea, transposed Nils Lofgren’s “Rose in the Heather” into an orchestrated guitar symphony, and transfigured Boudleaux Bryant’s oft-covered “Love Hurts” (Roy Orbison, the Everly Brothers, Gram Parsons and Emmylou Harris, etc.) into a cathartic power ballad that has since become their own.

Hair of the Dog was rounded out by the more subtle blues of “Whiskey Drinkin' Woman" and the haunting, dark-side-of-Pink Floyd that was “Please Don't Judas Me,” thereby giving fans a wealth of inspired music to sink their teeth into, without worrying over whose dog would provide the hair. Along the way, Hair of the Dog introduced Nazareth to an entirely new audience, as “Love Hurts” shot to No. 8 in the U.S., No. 15 in the U.K., and No. 1 in countries like Canada, Norway and even South Africa.

Decades later, Nazareth’s best-known tune continues to appear in movies (Dazed and Confused, Detroit Rock City, etc.) and commercials (Southwest Airlines, Nissan, Gatorade), while Hair of the Dog’s mordant title track was famously covered by Guns N’ Roses.

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