Thanks to Peter S. Miller for that video from a Morris dance performance at Duwamish Cohousing earlier this week. He explained:

The group performed at Duwamish Cohousing, then went to Lincoln Park and danced around the troll. All for the Celtic Festival of Lammas/Lughnasadh.

First, if you haven’t heard of Morris dancing (we’ll admit, we hadn’t), here’s a detailed history. As for the festival, that too has a long history (here’s a short summary), but is generally explained as a harvest festival celebrated around August 1, also noting the coming transition from summer to autumn.