As children we called this flower cuckoo spit because the stems were usually holding a blob of white foam with a small wriggly thing inside. Now I know that the small wriggly things were froghopper nymphs.
The proper name of the flower is Lady’s Smock (Cardamine pratensis). There are many superstitions around picking the flower – it could cause thunderstorms or attract adders. A sound reason not to pick a bouquet of lady’s smock is that a bunch of froghopper nymphs would be making themselves at home in your house.