Word Origin & History
1590, from Fr., from It. joviale, lit. "pertaining to Jupiter," from L. Jovialis "of Jupiter," from Jovius (used as gen. of Juppiter) "Jupiter," Roman god of the sky. The meaning "good-humored, merry," is from astrological belief that those born under the sign of the planet Jupiter are of such dispositions.
In classical L., the compound Juppiter replaced Old L. Jovis as the god's name. Jovian, in ref. to the planet Jupiter, is from 1794.