Chaucer was the first to bring the word ambages (ambiguities) out of French into English. He used it to refer to his two-faced words, his words “with two visages.” Probably the first time he ever played a trick with two-faced words was in The Book of the Duchess. For 500 years the lines
A long castel with walles whyte,
Be seynt Johan! on a riche hil,
seemed to have no reason for existing.
Then a 19th century English clergyman understood them to contain references to Lancaster, Blaunche, John of Gaunt and the Earl of Richmond! When Walter W. Skeat, an early Chaucer scholar, saw this interpretation he said “It is easy—when you know it.” And, because he knew the poem so well, went on to apologize, “I certainly ought not to have missed this."
Blaunche, of the House of Lancaster, is the “Duchess” of the poem. John of Gaunt, who was the Earl of Richmond, had been her husband. By their marriage he became Duke of Lancaster. Upon the death of his beloved Blaunche, he commissioned Chaucer to write the poem. Skeat’s analysis concludes, “We now have a reason for introducing the above lines, which have hitherto seemed rather pointless.”
We’ll allow this early word-trickery to guide our thinking: if a line in Chaucer appears “pointless,” that’s when extra scrutiny needs to be applied!