Vulgar means coarse and lacking good taste. A vulgar joke, vulgar display, frankly vulgar.
It covers both rude language and showy bad taste, and the second is often a judgement about class rather than about anything else. In older usage it simply meant of the common people, with no criticism: the vulgar tongue meant the local language rather than Latin, and Vulgar Latin is the ordinary spoken Latin the Romance languages came from. Note vulgarity, and that vulgar fractions is an old maths term meaning ordinary ones.
1adjectivevulgarCoarse and lacking good taste.
“Her new house was full of vulgar gold statues and leopard-print sofas.”
2adjectivecommonOf the common people, in older use.
“Vulgar Latin is where all the Romance languages came from.”
vulgar is a quality of coarseness.
Latin vulgaris comes from vulgus, the common people. The word meant ordinary, and English added the contempt — which is a fairly complete record of how one class described another.
Proto-Indo-European
*welH-
Latin
vulgāris
Middle English
vulgare
English, today
vulgar
Built from
From Middle English vulgare, from Latin vulgāris, from volgus, vulgus (“mob; common folk”), from Proto-Indo-European welH-. Compare Welsh gwala (“plenty, sufficiency”), Ancient Greek ἁλία (“assembly”), εἰλέω (“to compress”), Proto-Slavic valъ.
Etymology from Wiktionary, CC BY-SA