I’m glad to see in this week’s British radio and television listings magazine, ‘Radio Times’, that the noun derring-do is still in use. In trailing a programme about the Dam Busters, it speaks of ‘the combinbation of audacity, ingenuity and derring-do involved in bombing German dams to flood the Ruhr valley’. Derring-do means, in the OED’s definition, ‘daring action or feats, “desperate courage”.’
As LanguageHat and others have explained, it has its origin in these lines from Chaucer’s ‘Troilus and Criseyde’:
Troylus was neuere vn-to no wight in no degre secounde,
In dorryng don þat longeth to a knyght.
(Troilus never stood in second place to any man in daring to do all that was expected of a knight)
A series of variations, misprints and misunderstandings in the work of subsequent writers, as well as incidental developments in the language, changed the spelling from dorryng don to derring-do, and changed the construction from a verb phrase to a noun phrase, and thus changed the meaning.
It’s a reminder of how a usage can become established in the language by chance. Those who regard almost any change in the language today as a sign of the ruin of English, and probably the end of civilisation as we know it as well, would, I imagine, not insist that we now abandon a usage endorsed by writers as varied as Spenser, Scott and Bulwer-Lytton.
As a bonus, take note of Chaucer’s double negative in Troylus was neuere vn-to no wight.