obsolete or colloquial superlative of bad (adj.), common 14c.-18c.

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. 

1760, perhaps an isolated use; common after mid-19c., from lyric + -ism.

"belonging to or including both sexes," mid-15c., epycen, originally a grammatical term for nouns that may denote either gender, from Latin epicoenus "common," from Greek epikoinos "common to many, promiscuous," from epi "on" (see epi-) + koinos "common" (see coeno-). English has no need of it in its grammatical sense. Extended sense of "characteristic of both sexes" first recorded in English c. 1600; that of "effeminate" is from 1630s.

c. 1300, "the people of a country, a community," from Old French comunalte, from comun (see common (adj.) as if from Medieval Latin *communalitas. A respelling of commonalty (late 13c.). Meaning "the common people" is attested from 1580s; that of "state or quality of being shared" is from 1954.

in writing, to indicate the common casual pronunciation of could have, by 1909.

common name of a work-horse or farm horse, 1596 (in "Merchant of Venice"), probably from diminutive form of Dob (early 13c.), the common Middle English familiar form of the masc. proper name Robin or Robert; the personal name being applied to a horse.

1620s, from un- (1) "not" + precedented. In common use from c. 1760.

mid-15c., to-pens, representing the common pronunciation of twopence (see two + pence).

a spelling of homogeneous that represents a common pronunciation, perhaps by influence of homogenize.