jalousie
n.
5Fr < It gelosia, lit., JEALOUSY: prob. so named from permitting one to see without being seen6 a window, shade, or door formed of overlapping, horizontal slats, or louvers, of wood, metal, or glass, that can be adjusted to regulate the air or light coming between them


Somehow the proposed origin above of the word doesn't make sense to me. Jealousy might make
someone want to peek in windows if they could do so without being seen, not the reverse.