What is the etymology or history behind the euphemism "The Troubles" for the unrest/civil war in Northern Ireland?
“The Troubles” is not a euphemism, that is the name for that specific ethnic and religious conflict. The “Flight of Wild Geese” is similarily, not a euphemism, but the name for a historic event. It is poetic, but most names attempt to be. Historically it is not the first period called “The Troubles” relating to Ireland, that phrase has been used to refer to periods of rebellion in Ireland going back to the 1600s at least (which resulted in the aforementioned Flight of Wild Geese). Ireland is not unique in this either, the period of Russian history after Tsar Ivan Grozny is also called the “Time of Troubles”, during which there was constant civil war, political instability and a lack of a true, recognized government. This usage of the word “troubles” to refer to political chaos is fairly old.