From Old English wuduweaxe.

woad-waxen (plural woad-waxens)

1. The leguminous plant Genista tinctoria, native to Europe.
   • 1898, Annual Report of the Secretary of the Board of Agriculture, Massachusetts State Board of Agriculture, Volume 45, Part 1897, page 273 ↗:

     The woad waxen (Genista tinctoria), common enough near Salem, is seldom found inland, and the same holds good for the barberry and privet, which grow so abundantly near the coast and which have probably been introduced for two hundred years.

• (Genista tinctoria) greenweed, greenwood, whin, wood-wash, woodwax, woodwaxen