Charmander may be based on a 1000+ year old misconception about the salamander.

Both Aristotle and Pliny the Elder believed that the salamander was capable of withstanding the heat of flames, and even had the ability to extinguish them. In Pliny's Natural History, the oldest surviving encyclopedia, a fairly accurate description of the salamander is followed up by claims that "This animal is so intensely cold as to extinguish fire by its contact, in the same way as ice does" (Book 10, Chapter 86). Later in the same work, though, he seems to view these supposed properties with more skepticism, claiming that "if it had been true, it would have been made trial of at Rome long before this" (Book 29, Chapter 23).

The connection between salamanders and fire persisted, however, and we can also find it in the Talmud, which briefly mentions the salamander as a creature actually produced by flames, whose blood could protect anybody smeared in it from fire. Even Leonardo da Vinci, one of history's greatest scientific minds, seemed content to echo the received wisdom on the subject, mentioning in his notebooks that the salamander "has no digestive organs, and gets no food but from the fire, in which it constantly renews its scaly skin."