get (something) into (one's) head(redirected from get it into their heads)
get (something) into (one's) head
To believe that something is true. Get it into your head: I'm in charge until mom gets home, so you have to listen to me. A: "Why is Johnny holding his breath?" B: "Well, he's gotten it into his head that holding his breath will make him taller."
get into one's head
Also, get or take it into one's head . Form an impression, idea, or plan. For example, What strange idea has she got into her head? or He took it into his head that you want to quit. [Late 1600s] Also see get through one's head.