heliotrope (n.)
"plant which turns its flowers and leaves to the sun," 1620s, from French héliotrope (14c.) and directly from Latin heliotropium, from Greek heliotropion, from helios "sun" (see sol) + tropos "turn" (see trope). The word was applied c.1000-1600 in Latin form to sunflowers and marigolds. Related: Heliotropic.