vulgar (adj.)

late 14c., "common, ordinary," from Latin vulgaris, volgaris "of or pertaining to the common people, common, vulgar, low, mean," from vulgus, volgus "the common people, multitude, crowd, throng," for which de Vaan offers no further etymology.

The meaning "coarse, low, ill-bred" is recorded by 1640s, probably from earlier use (with reference to people) in the meaning "belonging to the ordinary class" (1520s). Chaucer uses peplish for "vulgar, common, plebeian" (late 14c.). Related: Vulgarly.

What we have added to human depravity is again a thoroughly Roman quality, perhaps even a Roman invention: vulgarity. That word means the mind of the herd, and specifically the herd in the city, the gutter, and the tavern. [Guy Davenport, "Wheel Ruts"]

For Vulgar Latin, see here

Definitions of vulgar

vulgar (adj.)
lacking refinement or cultivation or taste;
the vulgar display of the newly rich
appealing to the vulgar taste for violence
Synonyms: coarse / common / rough-cut / uncouth
vulgar (adj.)
of or associated with the great masses of people;
a vulgar and objectionable person
Synonyms: common / plebeian / unwashed
vulgar (adj.)
being or characteristic of or appropriate to everyday language;
the vulgar tongue of the masses
the technical and vulgar names for an animal species
Synonyms: common / vernacular
vulgar (adj.)
conspicuously and tastelessly indecent;
full of language so vulgar it should have been edited
a vulgar gesture
Synonyms: crude / earthy / gross