explicit (adj.)

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" (from PIE root *plek- "to plait").

As a euphemism for "pornographic" it dates from 1971 (phrases such as sexually explicit are earlier). Related: Explicitness. "Explicitus" was written at the end of medieval books, originally short for explicitus est liber "the book is unrolled."