Hi,
I believe that Croup is the wrong definition for Frogg.
I found in Hooper’s Lexicon-Medicum of 1829 that Frog is defined as Aphthae. And Aphthae is defined as: Roundish pearl-colored specks or flakes in the mouth, on the lips, etc., terminating in white sloughs. They are commonly characteristic of thrush.
A good website for archaic medical terms is
www.antiquusmorbus.comBest Regards, Rumire