1610s, "open to the understanding, not obscure or ambiguous," from French explicite, from Latin explicitus "unobstructed," variant past participle of explicare "unfold, unravel, explain," from ex- "out" (see ex-) + plicare "to fold" (see ply, v.1). As a euphemism for "pornographic" it dates from 1971. Related: Explicitness. "Explicitus" was written at the end of medieval books, originally short for explicitus est liber "the book is unrolled."