Nebrija’s 1492 grammar was the first to treat a vernacular seriously

Evidence

In 1492, a year well known also for some other events, a Spanish humanist called Antonio de Nebrija published a grammar of the Castilian language. This, as far as I am aware, is the first time that anyone had treated a colloquial language seriously. He tried to establish rules, and launched the process by which the Castilian dialect became the Spanish language. — Bernard Lewis, From Babel to Dragomans, 151

Categorization

Category: Factual Claims

• DEFINE: Establishes the pivotal moment when a colloquial dialect was codified into a standard written language.
• ADDENDUM: Supports the theme in ‘Complaints About Immodesty Go Way Back’ about how cultural norms get codified into institutional form; also echoes the language-politics angle.

Related

• Europe’s vernaculars became codified written languages beginning with Castilian in 1492 (similarity 0.92)