This is a member of the buttercup family. The name is derived from the Latin chelidonia meaning swallow. It was said that the flowers bloomed when the swallows returned and faded when they left. In fact the celandine blooms earlier but nevertheless its name reflects it's reputation for being one of the first signs of spring.
This picture was taken in a shady part of the garden. It's a good year for celandines!
I'm so glad someone else is interested in derivations! I hadn't known that. They're so buttery aren't they (butter - derived from Ancient Greek bouturon - cow/ox cheese). This could run and run! Lovely picture, Sue.