While sightseeing in St Patrick's cathedral in Dublin the other day, the guide told us that an incident in the cathedral gave rise to the phrase 'chance your arm', which means to take a risk or have a go, even though the likelihood of success is slim.
One of the sights on display in the cathedral is a solid wooden door with a rectangular hole cut out of it (see picture here). It is called the Door of Reconciliation because it featured in a dispute between two of Ireland's most wealthy and influential Anglo-Irish families - the Butlers (Earls of Ormond) and the Fitzgeralds (Earls of Kildare). Sir James Ormond locked himself and some guards in the chapter house of the cathedral to take sanctuary. His enemy, the Earl of Kildare, tried to get him to negotiate a truce, but Sir James refused. Eventually Kildare cut a hole in the door and thrust his arm through. Luckily, Sir James inside shook the hand, rather than cut off his foe's arm! Wikipedia says that this event happened in 1492, but A Compendium of Irish Biography says it was 1512.
The linking of the event to the idiom 'chance your arm' makes a good story, but it is unlikely to be true. The first recorded use of the phrase in print in the OED is 1889, well after the event that is supposed to have spawned it. This phrase refers to a tailoring context. An 1899 citation explains the phrase as meaning 'to risk a court-martial' and lose your stripes (on the sleeve of your uniform). Moreover, although the Butlers (Ormond) were more 'Anglo' than Irish, the Fitzgeralds spoke and wrote Irish (see paragraph 331 of this page). It is not known which language the two men spoke through the hole in the door - but it may not have been English and probably did not include the words 'chance' and 'arm'.