From 點 ("dot, point; to light, to kindle; to touch briefly") + 心 ("heart"). First appeared during the Tang era, eg. from the Book of Tang:
Tang Zheng was the official for the Jianghuai region. (One day), after the servants prepared the morning meal, Tang's wife said to his brother, 'I have not finished doing my makeup. You can have some snacks (lit. refresh your hearts) before I am ready to eat.