Blaise de Vigenère
French diplomat whose name ended up on a cipher he did not invent.
Blaise de Vigenère (1523–1596) was a French diplomat and scholar who spent much of his career at court. In 1586 he published Traicté des chiffres, which describes a polyalphabetic cipher with a keyword. He did not invent it. Giovan Battista Bellaso had described essentially the same scheme in 1553, and the table of shifted alphabets goes back to Johannes Trithemius.
Vigenère's own contribution was the autokey variant, where the plaintext itself extends the key. His name stuck anyway, and for nearly three centuries the cipher was known as le chiffre indéchiffrable, the indecipherable cipher. Friedrich Kasiski broke it in 1863. Ciphers tend to be named after whoever explained them most clearly, not after whoever thought of them first.