vergescu
The white shield that was the mark of novice knights, especially in Arthurian legend.
historical, rare
xxijᵗʰ daye of Maie, there shall be a grene tree sett up in the lawnde of Grenwich parke; whereuppon shall hange, by a grene lace, a Vergescu Blanke, in which white shield it shalbe^([sic]) lawfull for any gentleman that will annswear this chalenge ensewing to subscribe his name.
Where it comes from
From Middle English [Term?], from Old French vierge escu (literally “virgin shield”). It was white because it lacked a background or devices, which celebrated accomplishments, of which the knight had none.
Adapted from the Wiktionary entry vergescu (CC BY-SA 4.0).