The name daisy come from "day's eye" because the flower is only open during the day and closes up at night. Another name is "Thunder flower" since it blooms in the summer when thundershowers are common.
In addition, the daisy is believe to keep away lightening. For this reason, it was also kept indoors. A common name in England for the flower is Bruiswort since the crushed leaves could be used for soothing bruised or chapped skin.