This expression alludes to a daisy reopening its petals in the early morning or to its welcome appearance in springtime. The freshness of daisies has been a literary commonplace since at least the late 14th century when it was used by Chaucer.
RELATED IDIOMS :
pushing up the daisies
dead and buried – informal
This phrase, a humorous early 20thcentury euphemism, is now the most frequently used of several daisy-related expressions for being in the grave. Other idioms include under the daisies and turn your toes up to the daisies : both dating from the mid 19th century.