der·ring-do / ˈdering ˈdoō/ • n. dated , humorous action displaying heroic courage: tales of derring-do.

derring-do action displaying heroic courage. The term comes (in the late 16th century) from late Middle English dorryng do ‘daring to do’, used by Chaucer, and, in a passage by Lydgate based on Chaucer's work, misprinted in 16th-century editions as derrynge do; this was misinterpreted by Spenser to mean ‘manhood, chivalry’, and subsequently taken up and popularized by Sir Walter Scott.

derring-do (arch.) feats of daring. XVI. Taken up from sixteenth-century prints of Lydgate's ‘Chronicle of Troy’, where derrynge do is misprinted for orig. dorryng do ‘daring to do’. Its currency in mod. writers is due to Scott's use of deeds of such derring-do (‘Ivanhoe’ XXIX).