Etymology
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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 Formerly much cultivated; since superseded by indigo.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.

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vitreous (adj.)
early 15c., "glasslike," from Latin vitreus "of glass, glassy," from vitrum "glass," which perhaps was so called for its color (compare vitrium "woad"). Vitreous humor attested from 1660s.
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Glastonbury 
town in Somersetshire, famous as a prehistoric site, Old English Glestingabyrig, Glastingburi (725), "Stronghold (Old English byrig, dative of burh) of the people (Old English -inga-) living at Glaston," a Celtic name, possibly meaning "woad place."
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