pin one's hopes on
Also, pin one's faith on. Put one's hope or trust in someone or something, as in She'd pinned her hopes on an early acceptance to the college but it didn't materialize. This term, dating from the 1500s, originated as pin one's faith on another's sleeve and may have alluded to the practice of soldiers wearing their leader's insignia on their sleeves. By the 1800s, however, it acquired its present form.