Why is the ninth month called September?
"turned toward the observer, frontal," 1650s, from Latin obversus "turned against, directed toward," past participle of obvertere "to turn toward or against," from ob "toward" (see ob-) + vertere "to turn" (see versus). According to OED, not in common use until the end of the 18th century. The noun, in reference to coins, medals, etc. (opposite of reverse), is attested from 1650s. Related: Obversely.