Langsec as in "the root of (many) vulnerabilities is bad input handling, leading to parse tree differentials" started in ~2007 with Meredith Patterson's Dejecto

Langsec as in "the root of (many) vulnerabilities is bad input handling, leading to parse tree differentials" started in ~2007 with Meredith Patterson's Dejector. This research led to using actual parsing frameworks everywhere and, in fact, directly inspired nom. However, this doesn't have much to do with the languages themselves being safe. That research is very old; Ada was an early attempt to tighten-down type systems for safer code, and I'm sure that even that had precedent.