Well, the article does not actually answer 'where do type systems come from?' (as in the type systems of programming languages) but 'where do type theories come

Well, the article does not actually answer 'where do type systems come from?' (as in the type systems of programming languages) but 'where do type theories come from?' (as in the foundations of mathematics). I think type systems would have been invented for programming languages even if the mathematicians had never bothered with type theory, simply because they are necessary. I mean treating an integer stored in memory as a string or vice versa is still not going to work no matter what foundations for mathematics one likes...