So I was at my sister's today and talking with her roommate and telling him about an ancestor from the 10th century (a bard who split the head of his landlord open over a rent dispute and then wrote a poem about it - I'll have to find and post the poem here) and said:
"He left Ireland in the eleventeenth century..."
There was silence as, at first, I didn't realize what I'd said. And then came the smirks. And then the giggles.
I will not live this one down.