His nekke whit was as the flour-de-lys;
Ther-to he strong was as a champioun.
(= His neck was as white as the fleur-de-lys / And he was as strong as a champion)
The fleur-de-lys is a stylized lily flower, common in French heraldry:
‘Champion’ in this sense is a very specific term— in the 1300s, in English law, a final appeal against a judgement could be made via a trial-by-arms— both parties would nominate a champion to fight for them. The idea was that God would assure victory to the rightful side. And you thought the legal system today was fucked up. These appeals were common, and Chaucer mentions them a lot (in The Knight’s Tale, The Parson’s Tale, for example.)
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