1
general::
Change one's mind, vacillate, as in Jean's been blowing hot and cold about taking a winter vacation. This expression comes from Aesop's fable (c. 570 B.C.) about a man eating with a satyr on a winter day. At first the man blew on his hands to warm them and then blew on his soup to cool it. The satyr thereupon renounced the man's friendship because he blew hot and cold out of the same mouth. The expression was repeated by many writers, most often signifying a person who could not be relied on. William Chillingworth put it: "These men can blow hot and cold out of the same mouth to serve several purposes" (The Religion of Protestants, 1638).
American Heritage Idioms
2
general::
Phrase(s): blow hot and cold
Fig. to be changeable or uncertain (about something). • He keeps blowing hot and cold on the question of moving to the country. • He blows hot and cold about this. I wish he’d make up his mind.
McGrawhill's American Idioms And Phrasal Verbs