derring-do
Concise Oxford English Dictionary © 2008 Oxford University Press:
derring-do /ˌdɛrɪŋˈduː/
▶noun dated or humorous action displaying heroic courage.
– origin C16: from ME dorryng do ‘daring to do’, misprinted as derrynge do and misinterpreted by Spenser; later popularized by Sir Walter Scott.
'derring-do' also found in these Oxford entries:

