woad n.

Old English wad "woad," also the blue dye made from its leaves, from Proto-Germanic *waidīn (source also of Danish vaid, Old Frisian wed, Middle Dutch wede, Dutch wede, Old High German weit, German Waid "woad"), which is perhaps cognate with Latin vitrium "glass" (see vitreous), but Boutkan considers it a substratum word. Formerly much cultivated; since superseded by indigo. French guède, Italian guado are Germanic loan-words.