There are a number of competing theories on how the "frog" nickname
came to be:
Here are six such theories from the web page "Archived French Frog
(1) Many French people enjoy eating frog legs.
(2) Clovis, an early Frankish king, adopted frogs as part of his
(3) France's national emblem, the Fleur de Lys, resembles a frog.
(4) England's Queen Elizabeth I had a French suitor whom she
affectionately called her "little frog.""
(5) The lands around Paris were swampy, so the peasants who dwelled
there were called "frogs" by the upper classes.
(6) At one time, French soldiers wore camouflaged uniforms and
Also see this explanation from the web site word-detective.com:
"'Frog' was indeed at one time a popular derogatory term for a French
person, though it didn't start out quite that way. Originally (around
1330), 'frog' was applied by Britons to almost any group they found
objectionable, and was aimed at both Jesuits and the Dutch before it
was decided in the late 18th century that the French, with whom
England was then at war, were the real 'frogs.'"
Some of the same theories mentioned above are repeated on the page
"Ask The History Doc: Why are the French called Frogs?" on bparis.com
Alse see some Usenet discussions of the matter, archived by Google
OT - FROG
search strategy: french, "called frogs", because
I hope this helps.