vulgar

From Middle English vulgare, from Latin vulgāris, an adjective built on volgus/vulgus, meaning 'the mob' or 'common folk,' ultimately from a Proto-Indo-European root reconstructed as *welH-.

The facts given trace only the descent from a word meaning 'common people' to the Latin adjective for 'of the common people'; no further shift in sense is documented here.

The same Proto-Indo-European root is said to connect to Welsh gwala ('plenty, sufficiency'), Ancient Greek ἁλία (halía, 'assembly') and εἰλέω (eiléō, 'to compress'), and Proto-Slavic *valъ — words clustered around ideas of gathering or massing together.