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It’s not clear when the Goidelic Celts first got to Ireland, exactly how they assimilated the people who were presumably there before, or if this experience was much different from that of the Brythonic Celts across the Irish Sea. Still, after the Romans failed to arrive (and they came close), things got hectic: Dublin is a Scandinavian name, and after the decline of Viking control came the Normans and then the Anglo-Irish. In a slide-illustrated lecture, “Ireland: Topography and a History of Invasion,” Irish historian John Buckley details these waves of cultural and linguistic influence, explaining how Irish place names reveal the country’s history. At 8 p.m. at the Ripley Center Lecture Hall, 1100 Jefferson Dr. SW. $13. For reservations call (202) 357-3030. (MJ)