This Alice in Wonderland quote comes from a scene where Alice talks to the Daisies.
In this adventure Alice walks into a garden with large flower beds bordered by daisies and a willow-tree growing in the middle. Alice wishes that the flowers could talk and becomes speechless when the Tiger-Lily actually answers her! (Fun fact: The flowers Alice meets include a tiger-lily, a rose, a daisy, a violet, and larkspur.)
Tiger Lily explains that all flowers can talk, but because most garden beds are so soft the flowers in them are always sleeping. This garden has a very hard ground and so the flowers are awake and can talk when they are addressed first.
Suddenly, all the daisies start talking and shouting at the same time and Alice shuts them up by whispering these scary words:
"If you don't hold your tongues, I'll pick you!"
