A vernacular or vernacular language is the native
Usage of the word "vernacular" is not recent. In 1688, James Howell wrote:
Concerning Italy, doubtless there were divers before the Latin did spread all over that Country; the Calabrian, and Apulian spoke Greek, whereof some Relicks are to be found to this day; but it was an adventitious, no Mother-Language to them: 'tis confess'd that Latium it self, and all the Territories about Rome, had the Latin for its maternal and common first vernacular Tongue; but Tuscany and Liguria had others quite discrepant, viz. the Hetruscane and Mesapian, whereof though there be some Records yet extant; yet there are none alive that can understand them: The Oscan, the Sabin and Tusculan, are thought to be but Dialects to these.
Here vernacular, mother language and dialect are already in use in a modern sense. According to