Carothers evaluated over eighty polyamides before chosing
nylon 6-6, so named because diamine and diacid each contribute 6
carbons to the polymer chain. DuPont chose not to register
“Nylon” as a trademark.
The names in the first list above are natural polymers, in
the second, commercial, and, in the third, names for imaginary
polymers that I invented.
See also in The book of science:
Readings on wikipedia: