Is it ensure, insure, or assure?
"transparent, translucent," 1610s, from Latin pellucidus "transparent," from pellucere "shine through," from per- "through" (see per) + lucere "to shine" (see light (n.)). Related: Pellucidly; pellucidity.
pellucid pel·lu·cid (pə-lōō'sĭd)adj. Admitting the passage of light; transparent or translucent.