My main man Martin F. informs me that the phrase "Hair of the dog (that bit you)" goes back further than I thought, beyond the days when sheeps' bladders could be employed to prevent earthquakes and all the way to Roman times. What you would do was bind some hairs from the dog that bit you over the wound and, voila, you were on the road to recovery. This absurd practice went on through the late 19th century, according to this web site. Of course I'm having a bad fucking day so the link to the "hair of the dog" discussion no longer works and I couldn't find same* searching through the site.
*Tersely spoken Charlie Chan was prone to that expression, "same." I hadn't seen any Chan movies until recently; I was spoiled by the first one I saw, "Castle in the Desert," which is classic. "Charlie Chan in Rio" and "Meeting at Midnight," however, are pretty awful. Among the problems plaguing the former is the extended screen time of spastic ("expensively educated offspring") "#2 son" Jimmy. The latter is so deplorable I don't know where to begin. The plot has more holes than Blackburn, Lancashire. But "Castle in the Desert" is great, with many funny Chanisms.