I found this on Wiki:
"Tony D'Andrea was the one of the first people to use celluloid to produce and sell guitar picks. In 1902 he came upon a sidewalk sale offering some sheets of tortoise shell colored cellulose nitrate plastic and dies, and eventually he would discover that the small pieces of celluloid he punched out with the
dies were ideal for picking stringed instruments.
[8] From the 1920s through the 1950s, D'Andrea Manufacturing would dominate the world's international pick market, providing to major businesses such as
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Fender, and
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[9] One of the main reasons celluloid was so popular as guitar pick material was that it very closely imitated the sound and flexibility of a tortoise shell guitar pick."
I don't know if the world famous Fender 351 shape originated with Tony D'Andrea or not, but I will try to find out. Just like so many Fender designs, the 351 shape is the most copied pick shape in history.