As has already been pointed out, קרפד is not a native Biblical Hebrew word, nor does it have any mentions in this corpus of Hebrew from many periods. However, it seems not to have been borrowed from French, though I would guess it was influenced by it.
The Talmud mentions קורפדאי (possibly from Persian for "porcupine"; I wasn't able to locate this in Persian lexicography), describing it as a "שרץ" which makes it likely a mole (Rashi "טלפא")
French crapaud comes from Frankish krappa, from which also grappe "hook." Apparently, the source of "crapaud" is not from the same source as the word קורפדאי in the Talmud
In 1959 Ben Yehuda still translated the word as mole (adding in a footnote that it may be from Hebrew קיפוד, which could be the only tie to Hebrew; compare the word שאנן which gained a ל in the phrase שלאנן ושלו).
Here's where I think the conflation happened. The Even Shoshan dictionary (published in 1964, no link since I can't find it on the internet) has the word קרפדה and defines it as a toad (and has no entry for קרפדאי or any other similar word). Interestingly, it doesn't mark it as a foreign word. I assume the dictionary (or whatever source the dictionary might have used) assumed that קרפדה was a native word because of the word קרפדאי ("mole"), but defined it as a toad because of the French word.
In short: קרפדה is not from the French "crapaud," but from the Aramaic (or Persian?) קרפדאי, possibly related to Hebrew קיפוד, meaning "mole" (or "porcupine"). The meaning "toad" was probably assumed as the meaning of the word, based on French "crapaud," sometime between 1959-1964. However, it's not a borrowing, but a conflation of meaning with an existing word.
